[objcmt] -objcmt-atomic-property & -objcmt-ns-nonatomic-iosonly are companion flags.
Ignore them when determining if some transformation was enabled.
[objcmt] Introduce "objcmt-white-list-dir-path=" option.

This options accepts a path to a directory, collects the filenames of the files
it contains, and the migrator will only modify files with the same filename.