Added log4j to core
Added some more systems
Clearing action targets when action has been performed
Added simple ECSResource class for a named resource
Added more testing
fixed travis yml
Made `Entity` final and added `isRemoved` method
Added `SpecificActionTargetSystem` for deciding if entities are targets
Refactored ResourceRetriever a bit to be able to throw NPE
Added Enchant systems for use with `PhrancisGame`
Rename PlayCostSystem -> UseCostSystem, added Enchanting to PhrancisGame