Added request creation and processing to role.py. This is used if you want to request to become a certain role for a group. For instance becoming a club member. The process request view will also be used to cancel outstanding invites might this be necessary. Patch by: Lennard de Rijk Reviewed by: to-be-reviewed

Benjamin Niemann <pink at odahoda dot de>: Main developer of Python target.
Clinton Roy <clinton.roy at gmail dot com>: AST templates and runtime.