Render some triggers

Important triggers such as trigger_changelevel, trigger_multiple, trigger_once,
trigger_hurt, trigger_push and trigger_teleport are now rendered as translucent
solids each with a different colour (except for trigger_multiple and
trigger_once, they have the same colour).
Added sv_sim_qg to simulate quickgauss

If sv_sim_qg 1 then every secondary gauss shot is a quick gauss shot.  We also
removed sv_dtap which has not been implemented anyway.
Added cheat cmds that alter health and armour