Set session properly in zhdk-auth-contr.; consolidate set_session

Squashed commit of the following:

commit 1b86cc6e99e0e98b32b61cf1f6e4b463087c7f89
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Aug 19 15:43:21 2014 +0200

    Return user object form zhdk-auth/create_or_update_user

commit 7debd8aff069ad8f6b95242d8c1c9169f0168ba6
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Aug 19 15:31:41 2014 +0200

    Resolve naming conflict with rails

commit 0db1009a846313c3286ec27f3765aa0868534b3a
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue Aug 19 15:25:02 2014 +0200