properly delete a room

When accepting a LDAP filter (must still be a valid LDAP filter!) that gives out no users, it will kick all users in a room, albeit in a random random order. That can "de-auth" a room, where the admin-user leaves the room first, leaving the room in a half-abandoned state.

Since it is possible, that a user sets an empty LDAP filter, we dont want to instantly delete the room. Instead, set a flag in the config like: delete_permanently: yes/no that deletes the room, regardless of the LDAP filter

also, a room with 0 members (e.g. with an empty LDAP filtering), we have the problem that the previously existing alias cannot be reused? matrix_sync.matrix_client - INFO - Retrieved 0 members for room !xjYwaPWxOfbJVRPyNE:matrix-q.it.tuwien.ac.at)