Support for modes and flags based on project affiliation

[Fuchs]

As operator / channel owner I'd like to add channel access entry, or invex or exempt entry, which matches all users with a certain level of affiliation to my group, whether or not they are wearing my group's cloak.

Example use case: adding an invex to an invite only channel for everybody who is affiliated with my group.

Further reading: discussion in #freenode-gms, 2016/02/15, 22:15 UTC