Squashed commit of the following:

commit 85043af59846edd54b6f402829a698142fdb412f
Author: Michael Gapczynski <mtgap@owncloud.com>
Date:   Sat May 25 11:25:43 2013 -0400

    Clear opcode caches after writing to the config file, fixes #3372

commit e96ca0a217112a612e5018fb06115879be634f0b
Author: Michael Gapczynski <mtgap@owncloud.com>
Date:   Fri May 17 11:15:53 2013 -0400

    Add undefined verision variables

commit d7faeea0b8a79bcd84255120e396280fe62c8aa1
Author: Michael Gapczynski <mtgap@owncloud.com>
Date:   Tue May 14 09:34:01 2013 -0400

    Turn off theme before update

commit f620df4e88201a8d35ecb6173f258d5e5f67c7f9
Author: Bart Visscher <bartv@thisnet.nl>
Date:   Tue Apr 16 08:07:44 2013 +0200

    Also check for needed upgrade in the Sabre Maintenance connector

commit 223cfce8c89663beb95cf7438f47cea4bac6e0de
Author: Bart Visscher <bartv@thisnet.nl>
Date:   Tue Apr 9 21:05:11 2013 +0200

    Connect watcher failure function to the failure signal

commit 49b9a1e8af062c03ebc863e1139ca310944b784a
Author: Bart Visscher <bartv@thisnet.nl>
Date:   Tue Apr 9 20:51:43 2013 +0200

    Move start of the maintenance mode to the ajax call

    Make sure the update page is shown in a browser. And not an ajax request