remove changing the item type during game
Make game::revive_corpse check if the spot for reviving is empty.

Prevents debug message that another zombie is already there.
Changed all calls to revive_corpse to check for the return value and handle non-reviving.
Exit the adv. inv. after starting an activity
partially rewrite how field and item symbols are display on the map

fixes some inconsistencies, and an exploit
apply boomered/night vision/low light last
Merge bugfixes from BevapDin.