Draft: Improve permission checks and logic

• Fix rolify with_role to be combineable into larger queries without using .ids
• Add option to define rolify relations easily as has_many relations on models.
• Update associatable with the increased flexibility to let ActiveRecord combine queries better.
• Make use of hashes rather than .ids in the ability to prevent queries on load and allow CanCanCan to do its job better
• Add extension to CanCanCan to allow joining can definitions with scopes together

TODO:

• Check whether using .select(:id) in the ability makes better queries than the left-over id: ....ids.
• Check performance of new roles queries (left outer join) and determine whether its better to use scopes.
• Convert more of the ability file to use scopes.

Relates to #81