New powerloss/gain options

Added new config options:
- powerPerPVPDeath - Power lost when killed by another player.
- powerPerMobDeath - Power lost when killed by any mob.
- powerPerDeath - Power lost for any generic or unknown death (starvation, drowning, suffocating, falling, etc)

- powerGainedPerKill - This is the power a player will gain by killing another player.