Change $RCOptions_submit to not be a global variable
Refactor setting normalisation

* Normalisation is now centralised and abstracted away from
  inline DOM event handlers.

* Due to the nature of the old implementation, the guards could
  be trivially bypassed by using a permalink.

* MassPatrol/Userfilter was previously only enforced when clearing
  a user filter, and if there was no user filter to begin with,
  one could just enable MassPatrol. This has been fixed.

* Confirmation for enabling AutoDiff has been removed.

* The MassPatrol and AutoDiff settings no longer by pass the
  regular form submission don't apply until you press Apply (
  similar to the other settings). Though I liked the direct
  behaviour of them, it's a small loss for a larger gain in
  reduction of code complexity. Though I don't like giving up
  UX flow for simpler code, in this case it also makes room for
  a different UX flow that I find more important, which is that
  one should be able to submit the form without a warning.
  Now the user can enter the user filter and then enable MassPatrol
  without getting a warning (that would undo their action) if
  they do it in the "wrong" order.

Misc:
* Rename legacy krRTRC_RCDayHead to buildRcDayHead.

Fixes #15.