Eclipse autu-cosmetics in DistortionCorrection
externalized DistortionCorrection.run to enable calling without UI
fixed bug in generation of alphamasks

Thanks to Albert Cardona
threadsafe Utils.ensure(File)

There is a race condition in File.mkdirs() that makes it fail if another
thread attempts to generate the exact same directory simultaneously.
This does not happen frequently and thus remained undetected for a long
time, but it reliably screws up large and complicated alignments on beefy
workstations.  Bug reference

http://bugs.java.com/view_bug.do?bug_id=6492293
auto-finalize constant properties and parameters in Utils
parallelized intersection tests for pairOverlappingTiles

comes in handy when masks and coordinatetransforms are involved which is
when intersection tests are expensive
auto-removed some trailing whitespaces
added run method that does not need a worker for easier batch-mode useage

fixed visibility of run method

fixed NPE when fixed tiles list was empty
auto-removed some training whitespaces