Remove existing auth system from server, other cleanup.

* Remove all functions from mpt_cgi.py about logins/accounts/passwords.
* Adding the forced redirection back into uqauth.py
* Allow for both GET and POST requests from the client (not that it really matters)
Add a decorator and exception types to manage actions in the cgi script.

The @action decorator manages different types of actions, extracting arguments out of forms, and checking admin privileges.
Fixing the main() function of the server, other fixes.

"Other fixes" include:
* Requests should only attempt to log in if required by the server's response.
* A bug in checking required arguments