Revert "bugfix for #1098 (assigning a group to a user, the group appears incrementally many times the more you assign it)"

This reverts commit 265d7e50.

bugfix for #1098 (assigning a group to a user, the group appears incrementally many times the more you assign it)

Conflicts:

	lib/template.php

check during ownCloud upgrade if all the installed apps are compatible with the new ownCloud version. Disable them if not

show a label if an app is an internal app or a third party app from the app store.
show a preview image of the app if available

Fixes: http://bugs.owncloud.org/thebuggenie/owncloud/issues/oc-303

after editing a user quota, set the value of the quota field to how the server parsed the input, not the user input

this way the user can see when an invalid input is given

after editing a user quota, set the value of the quota field to how the server parsed the input, not the user input

this way the user can see when an invalid input is given

Changed multiple select for days of weekend to 'chosen'. Cleaned up some code. Removed success message when changing timezone.