Fixes #5221: Adds a helper method to allow a model instance to inquire if the instance is authorized for a particular permission.

Model instances can be asked directly if they are authorized for a particular
permission by, for example, calling 'instance.authorized?(:view_model)'. This...

fixes #812 - new permissions model, user group role and nest support, role filters for better granularity

• Daniel Lobato <elobatocs@gmail.com>
• Joseph Magen <jmagen@redhat.com>
• Tom McKay <thomasmckay@redhat.com>
• Greg Sutcliffe <gsutclif@redhat.com>...