Enhancements to PermissionMapper, RoleMapper, RoleDecoder

Change RoleMapper, RoleDecoder, etc. to return new interface Roles which is iterable & has contains() method. Add chaining & etc. capabilities.

Change PermissionMapper to return new interface PermissionThing (come up with a name), which only has implies(Permission) & maybe default method checkPermission.

Change RoleDecoder to accept AuthorizationIdentity.

Change PermissionMapper to accept SecurityIdentity instead.

Add stuff to SecurityIdentity.