Package and load assets from application package instead of firebase

[evshi]

Ensemble fetches all artifacts for an app from firebase. However, assets like fonts can be packaged with the app to avoid refetching and improve performance. We should be able to fetch remote artifacts and read assets from the local app package.

Technical notes:
We will be adding a manifest for studio to map artifacts and local file names. This may be leveraged to read local app assets as well.

Build process will need to put the assets into the right place and update manifest where to find them

[evshi]

cc: @kmahmood74