[SPARK-13843][STREAMING] Remove streaming-flume, streaming-mqtt, streaming-zeromq, streaming-akka, streaming-twitter to Spark packages

## What changes were proposed in this pull request?

Currently there are a few sub-projects, each for integrating with different external sources for Streaming.  Now that we have better ability to include external libraries (spark packages) and with Spark 2.0 coming up, we can move the following projects out of Spark to https://github.com/spark-packages

- streaming-flume
- streaming-akka
- streaming-mqtt
- streaming-zeromq
- streaming-twitter

They are just some ancillary packages and considering the overhead of maintenance, running tests and PR failures, it's better to maintain them out of Spark. In addition, these projects can have their different release cycles and we can release them faster.

I have already copied these projects to https://github.com/spark-packages

## How was this patch tested?

Jenkins tests

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #11672 from zsxwing/remove-external-pkg.

1 files changed, 0 insertions, 74 deletions

diff --git a/external/zeromq/pom.xml b/external/zeromq/pom.xml
deleted file mode 100644
index f16bc0f319..0000000000
--- a/external/zeromq/pom.xml
+++ /dev/null
@@ -1,74 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!--
-  ~ Licensed to the Apache Software Foundation (ASF) under one or more
-  ~ contributor license agreements.  See the NOTICE file distributed with
-  ~ this work for additional information regarding copyright ownership.
-  ~ The ASF licenses this file to You under the Apache License, Version 2.0
-  ~ (the "License"); you may not use this file except in compliance with
-  ~ the License.  You may obtain a copy of the License at
-  ~
-  ~    http://www.apache.org/licenses/LICENSE-2.0
-  ~
-  ~ Unless required by applicable law or agreed to in writing, software
-  ~ distributed under the License is distributed on an "AS IS" BASIS,
-  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  ~ See the License for the specific language governing permissions and
-  ~ limitations under the License.
-  -->
-
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-  <modelVersion>4.0.0</modelVersion>
-  <parent>
-    <groupId>org.apache.spark</groupId>
-    <artifactId>spark-parent_2.11</artifactId>
-    <version>2.0.0-SNAPSHOT</version>
-    <relativePath>../../pom.xml</relativePath>
-  </parent>
-
-  <groupId>org.apache.spark</groupId>
-  <artifactId>spark-streaming-zeromq_2.11</artifactId>
-  <properties>
-    <sbt.project.name>streaming-zeromq</sbt.project.name>
-  </properties>
-  <packaging>jar</packaging>
-  <name>Spark Project External ZeroMQ</name>
-  <url>http://spark.apache.org/</url>
-
-  <dependencies>
-    <dependency>
-      <groupId>org.apache.spark</groupId>
-      <artifactId>spark-streaming_${scala.binary.version}</artifactId>
-      <version>${project.version}</version>
-      <scope>provided</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.apache.spark</groupId>
-      <artifactId>spark-streaming-akka_${scala.binary.version}</artifactId>
-      <version>${project.version}</version>
-    </dependency>
-    <dependency>
-      <groupId>org.apache.spark</groupId>
-      <artifactId>spark-core_${scala.binary.version}</artifactId>
-      <version>${project.version}</version>
-      <type>test-jar</type>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>${akka.group}</groupId>
-      <artifactId>akka-zeromq_${scala.binary.version}</artifactId>
-    </dependency>
-    <dependency>
-      <groupId>org.scalacheck</groupId>
-      <artifactId>scalacheck_${scala.binary.version}</artifactId>
-      <scope>test</scope>
-    </dependency>
-    <dependency>
-      <groupId>org.apache.spark</groupId>
-      <artifactId>spark-test-tags_${scala.binary.version}</artifactId>
-    </dependency>
-  </dependencies>
-  <build>
-    <outputDirectory>target/scala-${scala.binary.version}/classes</outputDirectory>
-    <testOutputDirectory>target/scala-${scala.binary.version}/test-classes</testOutputDirectory>
-  </build>
-</project>