now supporting method calls as sources
#1: added JavaDoc comments
#2: refactored backwards solver
#3: optimizations for static fields (work in progress, unsound at the moment)
added a more complex test case for static fields
Merge branch 'develop' of github.com:secure-software-engineering/soot-infoflow into develop-implicitFlows

Conflicts:
	src/soot/jimple/infoflow/InfoflowProblem.java