#668 Ignore the UnusedModifier PMD test

[Egon Willighagen]

There was some discussion about this some time ago, and do not remember (convincing) reasons to keep these warnings, so I like to disable these UnusedModifier tests:

http://pmd.sourceforge.net/pmd-5.0.1/rules/java/unusedcode.html#UnusedModifier

They now cloud the statistics, and it's never been a CDK policy yet to comply to these habits. E.g. it would remove all these:

http://pele.farmbio.uu.se/nightly-jcp/pmd-unused/render.html

Consider this patch as a force to resolve the discussion.

[John May]

Applied and pushed.