HUGE performance update: Made DarkRPVars MUCH more efficient.

This has consequences: from now on you should register your DarkRPVars. If you don't, you'll get nagged about it.
You can still do everything your own way, but that'll be much less efficient.
Please read the wiki on DarkRP.registerDarkRPVar
Set DarkRPVars to nil instead of false

More efficient for DarkRPVars