Merge pull request #1 from victorlevasseur/master

Fixed a bug with force average expression, good catch @victorlevasseur :smiley:
Changed internal representation of a game.
Switched to JSON and dropped XML as well as jQuery.
Also removed generated documentation from the git repository.
Merge branch 'master' of https://github.com/4ian/GDJS
Forgot to export the game data when exporting for the web
Fixed runtimeGame.getInitialObjectsData
Switched all classes to prototypal inheritance
Performance seems better in Collisions Benchmark.
TODO: Doc not updated.
Added instance cache to recycle deleted instances.
Adapted RuntimeObject to avoid recreating members objects if not needed.
Some classes still needs recycling ( gdjs.Polygon... )
Various optimizations
Avoid arrays creation in polygon.js
Textures of SpriteRuntimeObject were always updated even when not necessary.
Avoid variable creation/destruction in variablescontainer.js.
Avoid calling Array.remove when running an object or automatism condition.
Various micro optimizations.
And ensure the canvas has the focus on IE9.
Optimized scene and global variables lookup when the variables are declared.
Added benchmark for variables.
Automatisms were broken.
Refactoring of index.html.
Fixed touch events.
Fixed error in RuntimeGame.
Fixed mouse and touch events position.
Implemented support for Web Storage ( See built-in "FileExtension" ).
Also changed licenses in extensions description.