Added McMMOPlayerVampirismEvent

Expands API possibilities regarding death penalty features.
Added McMMOPlayerPreDeathPenaltyEvent and McMMOPlayerStatLossEvent

McMMOPlayerPreDeathPenaltyEvent is fired before hardcore calculations
take place, use this if you want to cancel hardcore penalties.

Use McMMOPlayerVampirismEvent and McMMOPlayerStatLossEvent when you
want to know how many levels or experience the player lost or if you
want to modify this.