Implemented End Turn Button  (Issue #17 - enhancement)

InputOutput Changes:
Added declarations for the end turn button and gameobject
Assigned the method to call when the end button is clicked (within
instantiateUI())
Created method for changing the playerturn when the end turn button is
clicked
Created method for changing the interactable state of the end turn
button from the Game class
Cleaned up some commenting

Game Changes:
Added calls to check and change the state of the end turn button from
anywhere where the game state is changed (edits have been marked with
comments)
Merge remote-tracking branch 'origin/master'

Conflicts:
	Assets/Code/Game.cs
Conflicts were just within comments