Roles with preassigned "grants"

[optimumtact]

Building on the work in #11

If would be excellent if the authentication system understood the concept of a "role" that is a series of grants, any user who has "role" inherits automatically all the grants tied to that role.

The system should ship with some basic role archetypes, root, operator, halfop/mod, user, ignored - these will always be present and module authors can automatically add their grants to these archetypes (make the simple cases default and easy)