Cache.checkKey added - allows you to pass in a Cache type and a key and return a boolean.
Cache.checkCanvasKey(key) - Check if a Canvas key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkTextureKey(key) - Check if a Texture key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkSoundKey(key) - Check if a Sound key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkTextKey(key) - Check if a Text key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkPhysicsKey(key) - Check if a Physics key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkTilemapKey(key) - Check if a Tilemap key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkBinaryKey(key) - Check if a Binary key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkBitmapDataKey(key) - Check if a BitmapData key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkBitmapFontKey(key) - Check if a BitmapFont key exists in the cache (thanks to @delta11 for the proposal)
Cache.checkJSONKey(key) - Check if a JSON key exists in the cache (thanks to @delta11 for the proposal)