Re-architecture of CLI Build

[kitsonk]

Enhancement

The current structure of our build commands is around the tooling and not around the actual application. @matt-gadd has suggested that we re-architect and restructure the commands to align more to their use. Specifically we should have:

• A command that builds an application.
• A command that builds a library (maybe a widget library).
• A command that builds a stand alone Web Component.
• Possibly other commands.

We shouldn't care about what the tooling is used to get to that outcome.

[kitsonk]

There are a couple issues being addressed under this, so converting to an epic and linking in other issues.

[agubler]

The re-architecture is complete with dojo/cli-build-app and dojo/cli-build-widget, further enhancements or issues are tracked in their respective issues.