add "dandelion-api" as a module
Add Storage Unit for Asset as Public API

- definition of an asset
	/ name, version, type, content access (remote, local)
- storage by scope
- scope heritage
- override between scopes
- manage conflict on store or on demand
Transform AssetManager into a JsonAssetLoader

- use Asset Storage Unit to deal with asset storage
- manage hierarchical scopes for a unsorted scan