refactor controllers, change module prefix to `chatspaces`

I'm still working on this PR, but thought it'd be good to get some early feedback.

I thought it was confusing that the modules were prefixed with `chatspace` when all of the docs refer to the app as `chatspaces,` so I updated the module names accordingly. I also moved some of the controllers out of the single `controllers.js` file as the start of some larger refactoring.

What do you think of this direction?