Fix: Refugees using droppods inappropriately

- Tweak: visitor leave message
- Tweak: joining after rescue is somewhat less likely now
- Fix: guests respect forbidden stuff in more situations
- Fix: visitor groups now spawn with enough food

- Hotfix: Wanderer not spawning
- Fix: Guests complaining about lack of beds, while in bed

- Hotfix: GetRoom() error from A15.1280

- Tweak: refugee and joining wanderer events slightly more likely
- New: refugee and joining wanderer are picked from pool of related characters
- New: joining wanderer can be declined

- New: instructions
- Fix: visitors not coming while having prisoners (yikes!)
- Fix: drug policy error
- Fix: error when browsing wares with too many visitors

Updated for A15:
- New: Visitors will not leave bought items anymore
- New: More thoughts supported
- New: Guests will be unhappy if there are no guest beds, and more happy if there are enough