A simple caching system, used internally by [page:FileLoader].
			[example:webgl_geometry_text WebGL / geometry / text ]
			[example:webgl_interactive_instances_gpu WebGL / interactive / instances / gpu]
			[example:webgl_loader_ttf WebGL / loader / ttf]
		
To enable caching across all loaders that use [page:FileLoader], set
THREE.Cache.enabled = true.
		
		Whether caching is enabled. Default is *false*.
An [page:Object object] that holds cached files.
		[page:String key] — the [page:String key] to reference the cached file by.
		[page:Object file] — The file to be cached.
		Adds a cache entry with a key to reference the file. If this key already holds a file,
		it is overwritten.
		
		[page:String key] — A string key 
		Get the value of [page:String key]. If the key does not exist *undefined* is returned.
		
		[page:String key] — A string key that references a cached file.
		Remove the cached file associated with the key.
		
Remove all values from the cache.
[link:https://github.com/mrdoob/three.js/blob/master/src/[path].js src/[path].js]