Add option to ingnore NPC kills on feeds

[Depili]

I would be useful to have the same option to ignore NPC-only kills from feed syncs as with CCP api. Since sometimes a NPC killmail gets fed from eve-kill or somewhere else and atleast our board should be for pvp-kills only. Not a high priority suggestion, only if it's easy to do since deleting the odd mail or two each month isn't too much effort.