Extending Roles

Added the addition of parsing roles from UserRoles if a user has any assigned. Mainly this was need for my usage, as adding a new AD role / Group is extremely difficult to get done, and this will allow me to Authorize all users using a common AD role, but fine grain administrator / contributor policy using the internal Role Management of Orchard. Feel free to disregard this one if you have no use for it or do not believe it to be an addition that others will find useful. It just met the requirements I had.