move resource change logic to a separate class, keep AbstractWro4jMojo as simple as possible
move BuildContextHolder into ResourceChangeHandler
Create unit test for ResourceChangeHandler
add new tests & tweak TaskExecutor to propagate original exception instead of ExecutionException
don't track change informations about resources causing an exception
remove final modifier
fix failing unit tests
explicitly set parallelProcessing to false in setUp of the test
Merge branch 'issue792' into 1.7.x