Fixed a bug in FSEvents watcher resulting in contiguous file scans

This fixes the nasty issue that causes very often directory rescans - whenever
the '.csync_journal.db.ctmp' file is created/removed by owncloud itself,
FSEvents was sending us a notification about the *directory* whose contents was
changed and because it was a directory name but not a file name, it didn't
match any of the ignored paths (which it should've). That triggered rescan of
the directory to see what exactly has changed.

The fix is to ask FSEvents not to send us events if the file was modified by
the ownCloud process itself
Fixed ignored paths matching on OS X.

We now listen to changes to files and when an event is received we first match
the file name to the "ignored paths list" and only if the the file that was
changed didn't match figure out which directory needs to be synced.