Massive changes done to code base.

Level now fully owns enemies and towers, and handles the update and draw functions for them.
Added JavaDocs to some functions to clarify their purpose.
Cleaned up the code to make it easier to read.
Fixed errors with previous commit.
Inverted camera so that origin is at top-left as opposed to bottom-left.
Overhauled a lot of engine code and made towers draw their range.
Added code to find a target. Does not fully work yet.
Towers now find a target within range.
Fixed crash where pressing on white bar on top of screen would cause an ArrayIndexOutOfBoundsException.
Added optional debug variables to draw range and target line.
Created a separate gameplay state.
Merged branch "robert" with branch "Cole\'s-Branch"
Removed unneccesary code.
Enemies are now centered.
Adding MenuClass
Undid stuff
Towers can now kill enemies (way too quickly)
Merged branch "master" into branch "robert"
Merge branch 'robert' of https://github.com/siketh/COP4331_Project into robert
Merge branches 'master' and 'robert'
Merged branch "master" with branch "robert"