HG lock/unlock custom values

[CampbellCrowley]

Allow settings and customized values to be locked and unlocked using commands.

This would allow users with higher privileges to configure a game, but allow lower privileged users to run the games without needing to manage permissions for all of the commands.

This should probably be per-configuration/event-pack (#11 #34) to allow downloaded packs to be locked by default, and to lock specific packs created by users.