Fix MJDIFF-14: Support JDiff for test-sources 

git-svn-id: https://svn.codehaus.org/mojo/trunk/mojo/jdiff-maven-plugin@17944 52ab4f32-60fc-0310-b215-8acea882cd1b
Add test-classifier to descriptor when using test-sources

git-svn-id: https://svn.codehaus.org/mojo/trunk/mojo/jdiff-maven-plugin@17945 52ab4f32-60fc-0310-b215-8acea882cd1b
Rename JDiffDescriptorMojo to match goal

git-svn-id: https://svn.codehaus.org/mojo/trunk/mojo/jdiff-maven-plugin@17967 52ab4f32-60fc-0310-b215-8acea882cd1b
Refactor code, introduce BaseJDiffMojo class for shared code from both JDiffMojo and DesciptorMojo

git-svn-id: https://svn.codehaus.org/mojo/trunk/mojo/jdiff-maven-plugin@17968 52ab4f32-60fc-0310-b215-8acea882cd1b