Add user authentication and the simple form builder

This request includes an unusually large number of changes, as I spun off two feature branches from the accounts branch, then merged them in earlier locally without a clear pull request. 

In short, this includes:
- UI / API changes to support the authentication branch of the server
- A "first run" interface that prompts the user to add a default form to a survey
- A first stab at UI for advanced editing of surveys 
- Various refactoring and CSS changes to support the above

Again, rough, but comments will help get there.