Scaladoc class diagrams part 1

This commit contains model changes required for adding class diagrams
to scaladoc. It also contains an improved implicit shadowing
computation, which hides the shadowed implicitly inherited members
from the main view and gives instructions on how to access them.

This is joint work with Damien Obrist (@damienobrist) on supporting
diagram generation in scaladoc, as part of Damien's semester project
in the LAMP laborarory at EPFL.

The full history is located at:
https://github.com/damienobrist/scala/tree/feature/diagrams-dev

Commit summary:

 - diagrams model
   - diagram settings (Settings.scala, ScalaDoc.scala)
   - diagram model object (Entity.scala, Diagram.scala)
   - model: tracking direct superclasses and subclasses,
     implicit conversions from and to (ModelFactory.scala)
   - diagram object computation (DiagramFactory.scala, DocFactory.scala)
   - capacity to filter diagrams (CommentFactory.scala,
     DiagramDirectiveParser.scala)
   - diagram statistics object (DiagramStats.scala)
   - delayed link evaluation (Body.scala, Comment.scala)
   - tests

 - improved implicits shadowing information
   - model shadowing computation (ModelFactoryImplicitSupport.scala,
     Entity.scala)
   - html generation for shadowing information (Template.scala)
   - tests

Also fixes an issue reported by @dragos, where single-line comment
expansion would lead to the comment disappearing.

Review by @kzys, @pedrofurla.

Adapted to the new model and fixed a couple of problems:
 - duplicate implicit conversions in StringAdd/StringFormat
 - incorrect implicit conversion signature (from X to X)

Conflicts:

	src/compiler/scala/tools/nsc/doc/Settings.scala
	src/compiler/scala/tools/nsc/doc/html/page/Template.scala
	src/compiler/scala/tools/nsc/doc/model/Entity.scala
	src/compiler/scala/tools/nsc/doc/model/ModelFactory.scala
	src/compiler/scala/tools/nsc/doc/model/ModelFactoryImplicitSupport.scala

1 files changed, 6 insertions, 0 deletions

diff --git a/src/compiler/scala/tools/nsc/doc/model/comment/Comment.scala b/src/compiler/scala/tools/nsc/doc/model/comment/Comment.scala
index 914275dd8d..7b70683db5 100644
--- a/src/compiler/scala/tools/nsc/doc/model/comment/Comment.scala
+++ b/src/compiler/scala/tools/nsc/doc/model/comment/Comment.scala
@@ -108,6 +108,12 @@ abstract class Comment {
   /** A description for the primary constructor */
   def constructor: Option[Body]
 
+  /** A set of diagram directives for the inheritance diagram */
+  def inheritDiagram: List[String]
+
+  /** A set of diagram directives for the content diagram */
+  def contentDiagram: List[String]
+
   override def toString =
     body.toString + "\n" +
     (authors map ("@author " + _.toString)).mkString("\n") +