add themeing support and support for autoselection of mobile/tablet and standalone css/jss files and templates

The code for updating the principles table is still there. To make it easier to
revert this commit if that is necessary.

- Added some minor debug help to fscache

More checks for missing properties.

The thumbnails were already generated in this function, but now we save them
for displaying of the album.

Merge branch 'temp' into tanghus_contacts

Possible fix for cards with missing 'FN' property added through DAV.
Misc. UI cleanups.

Element menu didn't update.

Conflicts:
	apps/contacts/ajax/contactdetails.php
	apps/contacts/js/contacts.js

Fix missing 'N' or 'FN' fields on import.

Possible fix for cards with missing 'FN' property added through DAV.
Misc. UI cleanups.

Element menu didn't update.