[SPARK-5608] Improve SEO of Spark documentation pages

- Add meta description tags on some of the most important doc pages
- Shorten the titles of some pages to have more relevant keywords; for
  example there's no reason to have "Spark SQL Programming Guide - Spark
  1.2.0 documentation", we can just say "Spark SQL - Spark 1.2.0
  documentation".

Author: Matei Zaharia <matei@databricks.com>

Closes #4381 from mateiz/docs-seo and squashes the following commits:

4940563 [Matei Zaharia] [SPARK-5608] Improve SEO of Spark documentation pages

14 files changed, 31 insertions, 12 deletions

diff --git a/docs/_layouts/global.html b/docs/_layouts/global.html
index 8841f7675d..efc4c61293 100755
--- a/docs/_layouts/global.html
+++ b/docs/_layouts/global.html
@@ -7,7 +7,9 @@
         <meta charset="utf-8">
         <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
         <title>{{ page.title }} - Spark {{site.SPARK_VERSION_SHORT}} Documentation</title>
-        <meta name="description" content="">
+        {% if page.description %}
+          <meta name="description" content="{{page.description | replace: 'SPARK_VERSION_SHORT', site.SPARK_VERSION_SHORT}}">
+        {% endif %}
 
         {% if page.redirect %}
           <meta http-equiv="refresh" content="0; url={{page.redirect}}">
diff --git a/docs/bagel-programming-guide.md b/docs/bagel-programming-guide.md
index 7e55131754..c2fe6b0e28 100644
--- a/docs/bagel-programming-guide.md
+++ b/docs/bagel-programming-guide.md
@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Bagel Programming Guide
+displayTitle: Bagel Programming Guide
+title: Bagel
 ---
 
 **Bagel will soon be superseded by [GraphX](graphx-programming-guide.html); we recommend that new users try GraphX instead.**
diff --git a/docs/configuration.md b/docs/configuration.md
index 8b1d7598c4..4c86cb7c16 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark Configuration
+displayTitle: Spark Configuration
+title: Configuration
 ---
 * This will become a table of contents (this text will be scraped).
 {:toc}
diff --git a/docs/graphx-programming-guide.md b/docs/graphx-programming-guide.md
index e298c51f8a..826f6d8f37 100644
--- a/docs/graphx-programming-guide.md
+++ b/docs/graphx-programming-guide.md
@@ -1,6 +1,8 @@
 ---
 layout: global
-title: GraphX Programming Guide
+displayTitle: GraphX Programming Guide
+title: GraphX
+description: GraphX graph processing library guide for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).
diff --git a/docs/index.md b/docs/index.md
index 171d6ddad6..e006be640e 100644
--- a/docs/index.md
+++ b/docs/index.md
@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Spark Overview
+displayTitle: Spark Overview
+title: Overview
+description: Apache Spark SPARK_VERSION_SHORT documentation homepage
 ---
 
 Apache Spark is a fast and general-purpose cluster computing system.
diff --git a/docs/mllib-decision-tree.md b/docs/mllib-decision-tree.md
index fc8e732251..d1537def85 100644
--- a/docs/mllib-decision-tree.md
+++ b/docs/mllib-decision-tree.md
@@ -1,7 +1,7 @@
 ---
 layout: global
-title: Decision Tree - MLlib
-displayTitle: <a href="mllib-guide.html">MLlib</a> - Decision Tree
+title: Decision Trees - MLlib
+displayTitle: <a href="mllib-guide.html">MLlib</a> - Decision Trees
 ---
 
 * Table of contents
diff --git a/docs/mllib-guide.md b/docs/mllib-guide.md
index 39c64d0692..73728bb35e 100644
--- a/docs/mllib-guide.md
+++ b/docs/mllib-guide.md
@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Machine Learning Library (MLlib) Programming Guide
+title: MLlib
+displayTitle: Machine Learning Library (MLlib) Guide
+description: MLlib machine learning library overview for Spark SPARK_VERSION_SHORT
 ---
 
 MLlib is Spark's scalable machine learning library consisting of common learning algorithms and utilities,
diff --git a/docs/monitoring.md b/docs/monitoring.md
index f32cdef240..7a5cadc171 100644
--- a/docs/monitoring.md
+++ b/docs/monitoring.md
@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Monitoring and Instrumentation
+description: Monitoring, metrics, and instrumentation guide for Spark SPARK_VERSION_SHORT
 ---
 
 There are several ways to monitor Spark applications: web UIs, metrics, and external instrumentation.
diff --git a/docs/programming-guide.md b/docs/programming-guide.md
index 6486614e71..6b365e83fb 100644
--- a/docs/programming-guide.md
+++ b/docs/programming-guide.md
@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Spark Programming Guide
+description: Spark SPARK_VERSION_SHORT programming guide in Java, Scala and Python
 ---
 
 * This will become a table of contents (this text will be scraped).
diff --git a/docs/quick-start.md b/docs/quick-start.md
index bf643bb70e..81143da865 100644
--- a/docs/quick-start.md
+++ b/docs/quick-start.md
@@ -1,6 +1,7 @@
 ---
 layout: global
 title: Quick Start
+description: Quick start tutorial for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).
diff --git a/docs/security.md b/docs/security.md
index 6e0a54fbc4..c034ba12ff 100644
--- a/docs/security.md
+++ b/docs/security.md
@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark Security
+displayTitle: Spark Security
+title: Security
 ---
 
 Spark currently supports authentication via a shared secret. Authentication can be configured to be on via the `spark.authenticate` configuration parameter. This parameter controls whether the Spark communication protocols do authentication using the shared secret. This authentication is a basic handshake to make sure both sides have the same shared secret and are allowed to communicate. If the shared secret is not identical they will not be allowed to communicate. The shared secret is created as follows:
diff --git a/docs/sql-programming-guide.md b/docs/sql-programming-guide.md
index 22664b419f..350df9a731 100644
--- a/docs/sql-programming-guide.md
+++ b/docs/sql-programming-guide.md
@@ -1,6 +1,7 @@
 ---
 layout: global
-title: Spark SQL Programming Guide
+displayTitle: Spark SQL Programming Guide
+title: Spark SQL
 ---
 
 * This will become a table of contents (this text will be scraped).
diff --git a/docs/streaming-programming-guide.md b/docs/streaming-programming-guide.md
index e37a2bb37b..96fb12ce5e 100644
--- a/docs/streaming-programming-guide.md
+++ b/docs/streaming-programming-guide.md
@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Spark Streaming Programming Guide
+displayTitle: Spark Streaming Programming Guide
+title: Spark Streaming
+description: Spark Streaming programming guide and tutorial for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).
diff --git a/docs/tuning.md b/docs/tuning.md
index efaac9d3d4..cbd227868b 100644
--- a/docs/tuning.md
+++ b/docs/tuning.md
@@ -1,6 +1,8 @@
 ---
 layout: global
-title: Tuning Spark
+displayTitle: Tuning Spark
+title: Tuning
+description: Tuning and performance optimization guide for Spark SPARK_VERSION_SHORT
 ---
 
 * This will become a table of contents (this text will be scraped).