Refactored all entity-related things to entitymanager, and game over screen drawing to gameoverscreen. This would make it easier to start game after gameover by simply creating a new entitymanager. But it would be better to rename entitymanager to GameScreen, have both GameScreen and GameOverScreen inherit from a Screen class and then have the screens tell the game loop when they want to be changed to a different screen
Created screen class, made entitymanager and gameoverscreen subclass the screen class. The main loop now just deals with a 'Screen' and screens decide when to change screen by calling the changeScreen class in the main loop. So for example, gameoverscreen listens for enter and then changes to a new game screen. TODO: Should rename entitymanager to MainGameScreen.
Made sound stop properly, so it now works; also took out a few commented-out lines
Changed entitymanager.lua to maingamescreen.lua
refactored entity-removing methods for crowd and scary animal into single method, fixed some dangling references to entitymanager (which is now maingamescreen)
added a new parent_type to all entities; the parent_type now determines how entities are drawn by the MainGameScreen. If they are 'foreground' then a transformation is applied to put them on the background image path. If they are 'background' then no transformation is applied (to make sure that panicmeter, world and distance meter are not transformed). Not having a parent_type will throw an error
Made y-offset a local variable in maingamescreen instead of constant
Minor changes / took out commented-out code
made panicmeter a little neater by factoring out drawing of fill bar into drawFillBarFill and drawFillBarBorder and storing values in nicely-named variables in drawFillBar
dom/tyler - added player jump sound
Dom/Tyler - Rename sounds
Dom/Tyler/James/Craig - Added music playing. It doesn't work. About to merge Max's changes into master
Merge branch 'master' of https://github.com/twlevelup/syd-levelup-2-blue-team

Conflicts:
	main.lua