Allow Rapid to work in sandbox (no CDN)

[bhousel]

We've had a request to make Rapid work in a sandbox kind of environment behind a corporate firewall where it won't have access to fetch resources from the CDN. We should support this way of running Rapid.

I'm working on fixes now to get the Translations working again #206 , so while changing around how we package up all our data files, I'll see if I can get this in too.

[bhousel]

This landed in #1490
The way it works is that:

• Our old DataLoderSystem is now renamed to AssetSystem
• The AssetSystem can not track multiple "origins" to fetch assets from. We now support:
  • local - will only load assets from the local folder.
  • latest - may load latest assets from a CDN which match the expected semantic version
• You can control which origin the assets are fetched from prior to calling initAsync like this:
  

  Rapid/index.html

  Lines 45 to 48 in 82caae8

  	const context = new Rapid.Context();
  	context.containerNode = container;
  	context.assetPath = 'dist/';
  	// context.assetOrigin = 'local'; // test no CDN