Squashed and rebased rails4 branch on top of next

Squashed commit of the following:

commit 4e1edcee142b958883cec3f4f07c5fe672850a0e
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 12:26:20 2013 +0100

    Fix step in import

commit 25fd1e1bfc8f62db404e2677f4b717ce3e70ca5c
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 12:10:00 2013 +0100

    Fix setting type of imported media entry

commit 135c7e7c9a46a16f9155ecbe500e0cba7cd9b0a9
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 10:52:39 2013 +0100

    Added a bunch of try chains to prevent problems with not persisted meta_data

commit f283713dfb0a26a3f576151f2de626a0d79988e6
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 09:46:13 2013 +0100

    More media set controller refactorings

commit 9569d5421bd73d9f23d558e3aeb69f64a5fcc2ec
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 09:35:43 2013 +0100

    Refactored media set controller, wip

commit 7c1bb0786b0f5b8a97f9954d3c4da9e67e25c4c0
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 09:23:48 2013 +0100

    Fixing inheritable contexts (intermediate)

commit 5a2c4ebbffc6dd686d07d1ef2136b1950f216084
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Dec 10 08:55:41 2013 +0100

    ... wip

commit e8ae637ec0dcb041326c49a0c2c7e71fc76b26d1
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 9 13:57:49 2013 +0100

    Fixed several things wrt FilterSet

commit 0c9a3981f1160964f67fd669f5f42cc48c8c3fde
Author: Thomas Schank <DrTom@schank.ch>
Date:   Mon Dec 9 09:46:44 2013 +0100

    Merged and squashed rails4 on top of next

    Conflicts:
    	db/empty_medienarchiv_instance_with_personas.pgsql.gz