First round of fixes for FindBugs warnings

PR contains 2 things:
 * first is the exclusion of ANTLR-generated classes from the FindBugs analysis, as is does not make sense to fix issues there (generated code) and they would only clutter the final report
* second one is the fix for several dozens of warnings related to default encoding usage. Instead of platform dependent encoding UTF-8 is used.
Need to use the InputStreamReader, because FileReader does not offer a way how to specify the encoding.