More changes to SCP-173

- You can now manually set SCP-173's scare and neck snap sounds. Clears
up code a bit and allows more advanced gimmicks
- Clarified a few comments
- Snap damage now rand(120,150)
- Admin message now allows jumping to victims. You can use aghost to
follow SCP-173 otherwise
- Darkness check should be fixed (No longer includes unsimulated tiles
erronously, which sadly included tiles like the asteroid and maybe the
shuttle)
Merge pull request #1356 from dylanstrategie/SCP-173

More changes to SCP-173