Add menu for custom console variables

CV_RegisterVar({name = , defaultvalue = , flags = , PossibleValue = , func = }) -> CV_RegisterVar({name = , defaultvalue = , flags = , PossibleValue = , func = , category = , displayname = ,})

Changed menuname to displayname in case of future use (like better help command for example).

Added CV_NOMENU consvar flag. Automatically all cvars should be added otherwise.

cvar_menu_test.lua cvar_menu_stress_test.lua

Removed ghosts