Tie vision restrictions to player events

[etcadinfinitum]

Vision restriction choices seem random (because they are) -- tie this into a game mechanic better.

• When you hit a trap, when you take damage, etc you are blinded for 5s, and your upper vision limit is restricted slightly
• When you stray from the group, your vision decreases

[etcadinfinitum]

Closed in #85