Changes:
 - Added debug fps
 - Optimised objects.lua to only sort spawned objects when objects are added/destroyed, rather than 13 times a second
 - Made the menu an object, rather than a state, to allow it to exists both in-game and on the main menu
 - Separated update loop for camera into another object which runs AFTER the player's position has updated to fix an apparent choppiness in the player's position
 - Made some improvements to the menu while converting it to an object
 - Created gameMenu state
 - Renamed game state to gamePlaying state, also made some small improvements to it
Added placeholder menu.resetVariables function to stop variables persisting between menu spawns
objects.lua semantics