Add FindBugs support

[brarcher]

This adds support for the FindBugs java static analysis tool. It will scan the java source of the Android project and determine if any known bugs exist. To run this tool, use the following:

$ ./gradlew findbugs

It will output a HTML report with its findings. As of this writing, a few issues are identified. A sample report is attached here: findbugs.html.zip

If an issue is found and you want to ignore it, you can add exclusions to the exclude.xml file; a base file is included.

I've used this tool in my Android projects. I'm submitting this request, in case it may be useful to you as well. (:

[codekidX]

Thanks a lot for this @brarcher . I'll just research about this and add this to the repo !