[WFLY-1635] Add a new map-groups-to-roles attribute to allow users to configure if there is a 1:1 mapping between the two.

If set to false (The new default) then no mapping occurs and at the time of authorization mapping is expected to occur dynamically.
[WFLY-1635] Minor changes to map-groups-to-roles model handling from review comments.
[WFLY-1635] Switch the default map-groups-to-roles to true i.e. the existing default behaviour.

The ManagementRealm definitions with <authorization /> definitions then have this set to false.