Filter display of blacklisted files

Blacklisted files like ".htaccess" and ".git" should not only be
blacklisted for upload and rename, but they should also not be displayed
in the directory listings.

I needed this personally to hide ".git" folders in shared folders. Its
also a simple implementation of feature requests like
http://forum.owncloud.org/viewtopic.php?f=4&t=3279 and
http://forum.owncloud.org/viewtopic.php?f=3&t=5708