Start work on blindsense and Echolocation talent.

Work on FOV as part of this: properly clear seen tiles when running stops
or when talents change light radius.  Update FOV when inventory changes.

Add senses to character sheet.
Improve log messages to account for what's seen, etc.

Pull damage_types.lua's logic to handle this into new Actor methods
getLogName, getSrcName, getTargetName, and use them in Combat.lua also.

Add game.logSeen2 (taking 2 entities) and make sure that combat log
messages are shown if either participant is visible.

Cosmetic iprovements: Tweak blindsense's appearance. Better redraw FOV
if talents change it.
Blindsense now detects creatures, too.
Add blind-fighting.  Buff Echolocation and Dweller in Dark.

There's now a 50% miss chance against unseen foes, unless you have the new
blind-fight attribute.

Internal changes: Add Actor.canReallySee.  Tweak log messages for missile
combat with unseen foes.

Rename Echolocation to Bat-Blind Vision; Echolocation is a bit anachronistic.
Dweller in Darkness now grants extra regen if you have no light.  Improve
Blood Sip's particle effects and log messages.

Bugfix: right-click menu could reveal if a creature was present.