Updated ButtonSpawnController to reinitialise its button if it already has a button. Changed the Attack Button's "handleBattleEnd" method to simply deactivate itself until asked to reactivate; the old "handleBattleEnd" method's contents has been moved to the new method "prepareForRemoval". Some objects still require the prepareForRemoval method during the game, such as Shield type buttons.
Clarified explanation of the new handleBattleEnd method.
Merge pull request #8 from cgosingtian/buttonStore

Changed button destruction-recreation logic to reuse ("deactivate-reactivate")