Feature/ui dashboard setting

* Dashboard endpoints [Namespace aware]
* User Settings endpoints

The PR does not contain (will be added in future):
* ACLClient integration (Dashboard Read/Write access check)
* Namespace deletion hook --> Delete all dashboards belonging to that namespace when it is deleted.
this seems to be a bad design - to have extra table for differrent configuration type. Even more: we have two extra tables for that: to have incremental IDs..