As an Owner, I can define Space-specific Roles

(User Story, To be Fixed , Priority: Medium, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Access Control
Summary: A Role is essentially a set of Permissions. The built-in ones should be good enough for most purposes, but I should be able to tune my own versions, with greater or lesser rights.
These Space-specific Roles should be usable in all the same ways as the built-in ones: the mechanism, as usual, should play fair.