Upgrade rails to 4.0.5, fix related issues

also upgrade other gems

Squashed commit of the following:

commit 0a9aa395cf51cea8fc17c76b9000e95416b67e78
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue May 20 16:07:06 2014 +0200

    Fix yet an other permit probblem

commit cfe407f4115978c0e52d948ddc95b35f5d8574df
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue May 20 12:51:47 2014 +0200

    Fix filter set controller

commit 9f42dac76d24d4dc39297154e59304e355cd9f01
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue May 20 12:36:23 2014 +0200

    Fix perm params and more when updating arcs

commit 778c803761f72d9d3d9efd2fa2a071191abdf80c
Author: Thomas Schank <DrTom@schank.ch>
Date:   Tue May 20 11:58:23 2014 +0200

    Permit attributes in permission controller

commit 58c54f2ec54ed708f814e72d34935ebe85db66e0
Author: Thomas Schank <DrTom@schank.ch>
Date:   Fri May 16 15:24:42 2014 +0200

    Upgrade to Rails 4.0.5; upgrade gems
app: error handling: make custom Error Classes that can be `raise`d

Fixes the infamous `not_authorized` mess:
`raise UserForbiddenError` instead of `not_authorized!`
doc: dev guide: add informal spec about individual contexts aka vocabularies
Remove composite_primary_keys gem (prepare for rails 4.1)

and refactor madek so it doesn't need it