Rework the implementation to use loopback-workspace 3.0

Requires strongloop/loopback-workspace#56.

My intention is to fix the `TODOs` in subsequent pull requests, most of them require non-trivial changes in loopback-workspace.

/to @ritch please review
It would be nice maintain our convention of `TODO($user)` which makes it clear who is going to make sure it gets done or atleast we know who created the `TODO`.