Reduce code redundancy using a generator
Move code generating py file name fro ui file name to its own function.
Add --files= option to setup.py build_ui, to pass list of files to rebuild

Related to http://tickets.musicbrainz.org/browse/PICARD-566
Add missing whitelines.
Allow compilation of ui files in unusual directories.

.py file will be produced in the same directory of the .ui file
Drop time-stamp comparison, remove variable comments from generated files.

See discussion at http://tickets.musicbrainz.org/browse/PICARD-566
Restore time-stamp check, files depends too much on uic versions anyway

It works in most cases, and now one can force regeneration of one or more files
if needed.
Merge remote-tracking branch 'upstream/master' into build_ui_improvements
Update NEWS.txt
Merge pull request #266 from zas/build_ui_improvements

Add --files= option to setup.py build_ui