increased death toll's skybox resolution

Re-made No Mercy & Death Toll's skyboxes to better match Cry Of Fear.
Added in a missing exterior texture on Dark Carnival concert finale.

reworked l4d2 textures, further polish.

Huge update for l4d2 campaigns, mainly dark carnival.
Most of the l4d2 campaigns recycle the same textures, so this affects other maps too.
Remade the tunnel of love from scratch with whatever I could come up with in photoshop, not exactly cof textures but fuck it, i like the results. Swamp fever has been affected, most nature textures, changed a few overlay textures.

a tweak

Updating the first level of dark carnival (highway).

Added back the sewer slime texture in no mercy, fixed transparency issues.
Re-adjusted dark carnival skybox.
Minor tweak on death toll.

Polished no mercy a bit, finished up death toll.
Gave dead air some attention, nothing too fancy.

playing around with some ssbump textures

Fixed lots of poor texture blends on crash course and death toll.