Players now claims ownership of Units.
Reworked how ARMOR works. It now works as a damage reduction
shield that lasts the entire round (does not get removed
by damage). This helps differentiate it from HEAL.

Created two new ability effects, AddResourceEffect and
StealResourceEffect. AddResourceEffect adds x number
of random resources to the owner of the unit that
performs the effect.

StealResourceEffect checks if the owner of the targetted
unit has a (randomly chosen) resource. If not, it checks again,
this time omitting the first resource type, recurring until
there are no resource types left, or a resource is found.
If a resource is found, 1 is subtracted from the targetted
units owner's pool, and 1 is added to the source unit's
owner's pool. Effectively stealing one of the resource
from the other player.

Created a "cleanup step" via several methods in Game.
Called via cleanup().
Resets all units armor back to 0 via armorCleanup(Unit[] units).
Removes excess HP (HP over max from HEAL) via healthCleanup(Unit[] units).
healthCleanup also declares any units with 0 HP or less for dead.
Finally declares any player that has only dead units as game loser,
via checkForLoser method.

Created Thief unit, with relevant ability to steal resources.