No safe zones 6 minutes after murder

This request adds a piLastKillTime to players, which records the game time when they killed an innocent player. After killing an innocent, the murderer cannot enter a safe zone for six minutes. This is turned off during a frenzy. This will increase PvP by not having PKs able to hide immediately after a kill.

Note to commenters: this is intended to increase PvP between PKs and hunters. If you don't think this is a good idea, please state why you would like less PvP, or provide an alternative to this pull request that increases PvP. Comments about potential murderer-safe zones or issues with the timer, or exceptions I've missed are welcome.