disable/change companion API

[highno]

This is a feature request to give scripters the ability to control the players companion.
This could start at select a special companion in a special room (all players having a ballon follow them at party room, still different ballons to select from via script to let the script decide on e.g. teams for games).
It may also provide companion start/stop function (like cats and dogs need to stay out of a certain room) or even disabling companions on entering a room like a big auditorium which would be massively crowded even without companions already.