[WIP] MSM contract editor

Still very much a messy work in progress (lots of TODOs, commented code in new files, excess code from copied files, etc.)—could use a review for "is any of this risky to have in staging->level builder->potentially production" pipeline, with the plan to continue working on this and do a full style/fix review later.

![image](https://cloud.githubusercontent.com/assets/206973/4947067/942757ba-661d-11e4-915d-4f14cf71ea90.png)

![image](https://cloud.githubusercontent.com/assets/206973/4947068/973fb9d8-661d-11e4-936c-cdc06f82b3ab.png)