Adds bee swarms and butterflies and diseases to create them

Adds swarms of space bees, they sting you like spiders. Each bee is 0.5 toxin and 1 health. I'm not too familiar with lists so if there's a better way to handle their overlay update proc I'd appreciate being shown it.
![space station 13 2014-11-04 035809](https://cloud.githubusercontent.com/assets/4343468/4886330/6aeb18ea-637b-11e4-93dd-86bad360bedb.png)

Adds butterflies, they don't do much except look pretty.
![space station 13 2014-11-04 035843](https://cloud.githubusercontent.com/assets/4343468/4886332/6cc8ef34-637b-11e4-9705-926e387353c4.png)

Adds anxiety and updates beesease diseases to make you cough up butterflies and bees respectively.

Don't merge before #5545, this will be updated once that happens.