Fix #11

Remove undesired rules restricting admin's modifications to contests and polling groups once contests begin. These rules were added to maximize protection against a misbehaving admin, but the rules were overly restrictive, preventing most realistic use cases from being possible.

In order to make the system usable in a real world scenario, it is necessary to relax the rules against modifications once contests exist, trusting the admin to behave reasonably due to the fact that any chicanery on the live results will be provable from chain history.

Closes #11 (closed)