[#68517412] FIX: dont allow to change start date for option lines in case of take back

Squashed commit of the following:

commit 6b84a092aa3f32d6f88f34e0445a2666bc4fed01
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Fri Apr 25 16:26:50 2014 +0200

    test for not allowing to change start date for option lines in case of take back

commit 666d27d843ef4ad24dc5d79ea2b7c2ae289d28b7
Author: Matus Kmit <matus.kmit@zhdk.ch>
Date:   Wed Apr 23 13:24:44 2014 +0200

    FIX: dont allow to change start date for option lines in case of take back