UML

I have created a UML class diagram using ObjectAID UML, to improve
clarity on the design. Also corrected two minor typos, and removed an
unused import.
UML jpg

Added a .jpg for the UML, so people without objectAid can still view the
.jpg
Merge branch 'master' of github.com:DylanMeeus/JavaGame into DylanMeeus-master
Merge branch 'DylanMeeus-master'