New rooms in Sci and a public garden.

I hope I'm doing this right.
This adds a new public garden above the Arrivals shuttle, a Misc. Sci room next to Xenobio, a grenade testing
room below the bomb launching room, and an expansion to Xenobio Cell 6,
which should allow it to hold some nastier aliens than slimes.
![whydididothis](https://cloud.githubusercontent.com/assets/8294408/4055478/780caaa4-2da5-11e4-9f5c-fcb8a220afc4.png)