In preparation for addressing issue #83, refactor and clean up some of the code in the APIDocumentationDoclet.
Include the return type of the method in the text doclet.
Include the type parameters for parameterized return types.
Merge pull request #84 from DavidWhitlock/issue-82

Add return type in API documentation doclet.

In order to address issue #82, the return type of methods is not outputted by the `APIDocumentationDoclet`. I also added support for outputting information about the type parameters for method parameters and return type.