Add a reset waiver function to Kingdoms and Parks

[kenwalker]

Currently when a Kingdom or a Park wants to initiate a new waiver they first have to clear all the existing waiver status' on every player, a time consuming operation. Sometimes, by request, a jsork hack is run to do that on demand, but that's not really sustainable.

Add an option in the admin page for both Kingdoms and Parks that offers to reset the waiver status. This is a non reversible operation and such should have a dialog warning the user about the consequences of their actions.