Moving settings into Convars for console control. Added the option to not allow the grenade.

The settings were previously just hardcoded in and set into global
variables. If we set them as ConVars we can then set them via the
console.

For some reason the gameDescription.txt settings are not reflected on to
these Convars so it is probably best if you do not show them to people
as they will believe they do something!

Also; people had asked if it was possible to turn off the grenade launcher as some
people I play with felt this was "cheating" as you could run into a room of 30 props grenade .. guaranteed get a kill even if you die. It defaults to on so there would be no difference to normal games :)