Refactor much of the API testing code.

Refactor much of the API testing code.
Old: ApiWatchTest not only tested the watch module, but also tested the login module,
     and the login module test was also used to log in to the API for the other tests.
New: ApiWatchTest only contains watch-specific methods. The login testing has been moved
     to ApiTest. The code used to log in and get tokens have been moved to ApiSetup. Nice,
     organized, and much nicer than before. ApiUploadTest is still pretty fugly, though.