Various NetworkVar changes

Added ENT:CallNetworkProxies to fill in the functionality of
ENT:NetworkVarNotify

Removed useless argument in __index ( which could've caused problems
with the NWVars default return )

ENT:GetNetworkVars accepts an argument to also return entities in the
table, default behaviour still intact

Thirdperson and Cameradistance for vehicles now use NWVars