Gui in a seperate module (take 2)

Split out gui code (as much as possible)

Based on a previous pull request: I couldn't reproduce the test failures you saw back then, now I could (circular static initializations), so fixed those.

It's still a bit ugly that findbugs.xml (in 'findbugs') references the edu.umd.cs.findbugs.gui2.Driver class (in 'findbugs-gui'), but that doesn't appear to be fatal anywhere.