A major commit containing refactoring and continuing work on messaging.

Refactored the effects package directly into game (from abilities).

Added a HashMap in Player called UnitMap, to be able to fetch a Unit object by giving a unit name (string).

Messaging:

Created Target class.

Can now serialize a Player object (containing units and their targets) into a JsonPlayer object.

Can now serialize a Unit object (with it's targets) into JsonUnit object.

Can resolve a TargetsMessage with full functionality, tested with correct results through he combat engine.