Suggestion: add the option to separately disable mirrors maze and elevator shafts

[Meyers07]

While mirrors maze and elevator shafts are amazing, it might be pace-killing (mirror maze has a lot of invisible dead ends, and elevator shafts are overlooked by those not used with the ladder, a very uncommon engine platforming quirk in Doom) on maps where progression rely on crossing those. Not to mention the mirrors maze are performance killing. The other prefabs are great so maybe what it's required is only to disable those two pace-killing prefabs.

[GTD-Carthage]

The mirror mazes have a control for them under Prefab Control. If you have issues with these because of just performance though, you can play with the amount of mirror recursions by changing the CVar r_mirror_recursions. Setting it to 0 leaves mirrors to render with a nice environment map still as opposed to disabling them outright.

There is no control filter for the "liquid" ladder elevator yet but I'll look into that soon.