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've already released locally updated version so I changed to 1.3.1.
I will change to 1.4 but as long as you don't release it this should not change anything. Is that correct?