gDecals [Decal System] - Place images anywhere!

1. Decals no longer collide

1. Fixes error that would occur with Xenin addons

1. Added support for undoing of duplicates (hit Z to undo a duplicate)
2. Added remove decal command and C-menu option
3. Added render distance
4. Fixed decals having objects render behind them (lights behind the entities)

1. Fixes HUDs with DModelPanel's breaking ToPos() [Basically, freezing when editing the decal]

1. Adds clear command
2. Fixes decals not respawning

1. Adds a few extra checks
2. Added more convars

Initial version.