Add asset registry command, remove asset init and yeoman

[busma13]

This PR makes the following changes:

• Removes asset init command, yeoman-* dependencies, asset and processor generators and templates, and related tests
• Update registry generator to use ejs directly instead of yeoman-generator
• Add asset registry command to replace asset init --registry
• update AssetSrc.generateRegistry() to build index.ts registry file if in a typescript repo

Ref: #3559