create custom exception/error handling mechanism

As a follow up from #177 

Would like to spice up the frontend test only by adding one more level in the routes/contents created in the FixtureLoader to see both ancestor and parent suggestions.
Default is when no group was selected. All suggestions by those name would be merged into on list called default. When somebody uses a group that still exist i would suggest to just merge their suggestions together in one list (just one change in controller).  Doing that, somebody would be able to extend the List of of an other provider. What you do with the grouped list is up to you as you define the template. =