upgraded Findbugs, Checkstyle and PMD

- removed pmd library: now it is loaded from maven repo
- added pmd-java library into build.gradle so java rules are taken from repo not local custom jar
- upgraded Findbugs, Checkstyle and PMD, resolved problem with dependencies
- minor changes required by new PMD API
- better support in case when findbugs throws exception when there is no file for analyzing
I did not split PMD. You just merged it into one library:
http://search.maven.org/#search|ga|1|g%3A%22net.sourceforge.pmd%22

If I'm correct you need to pmd-java to have rules about java and you can add pmd-php to add rules for php. That's the comment about.