Clear faces after the event execution ends
Move the face cleanup to Game_Interpreter::CommandEnd()
Fix bug when face is set in common event or other event
Correct face handling with parallel processes

The following behaviour seems to mimic RPG_RT well:
a) parallel processes never clear faces; face sett in a parallel process
execution exists after it is ended (however, it can only be visible in
other parallel process's Show Message, or in events that use Wait command),
b) non-parallel events clear faces when their execution begins and ends.
Formatting: delete stray tabs
Merge pull request #342 from rohkea/faces

Clear faces after the event execution ends