Project space metadata

implements
https://docs.google.com/a/dimagi.com/document/d/1ZpdRZLSstmnW_ubertb2jAMphssyOct_kWQ8YhpOhA0/edit#heading=h.i0ohvkukphfh

Restricts permission to domain admins (superusers permitted)

I chose not to use tastypie, since it would have been a mess to integrate with non-django ORM data
out of curiosity did you consider using tastypie for this? it has pretty nice auth and versioning management out of the box which will be nice if we ever want to change this. also, i assume the exact structure of the spec is flexible and the author just made something up