minor changes on AssetsLocationWrapperSystem
AssetsLoaderSystem use ServiceLoader to load AssetsLoader

To configure a new AssetsLoader, you need to
- create a class who implements AssetsLoader
- add the canonical name in a file "com.github.dandelion.core.asset.loader.spi.AssetsLoader" in folder "META-INF/services"

You can develop your own AssetLoader or extends AbstractAssetsJsonLoader

AssetsNopLoader is remove