Extend RBAC to cover authorized events

The purpose is to allow nodes to finetune permissions to their specific needs. Also, this is necessary for any PUBLIC nodes.

[ ] A table with authorized events' role requirements
[x] A frontend for manipulating the roles for admin users
[ ] Initial generation of table to provide defaults? - or -
[ ] Uses (following) fallback roles from event class if nothing is found
[x] Authorized events need a 'roles' class attribute that provides default/fallback roles (Systemwide default: ['crew', 'admin'])
[x] Clientmanager checks permission before execution

Hackerfleet / hfos-legacy