added set (create/set a cvar) and seta (create/set a saved cvar) commands, now config...

added set (create/set a cvar) and seta (create/set a saved cvar) commands, now config saving uses seta, and this allows mods to add their own cvars in default.cfg easily
cleaned up some of the command/cvar startup sequence, the menu commands and cvars were being registered AFTER config loading and video init, now they're registered before like they should be
cleaned up some cvar code and added developer printing of the more important cvar calls

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@4514 d7cf8633-e32d-0410-b094-e92efae38249