Unified lib+loco new + new starter generator

[jondot]

In this release we will be moving from a standalone loco-cli project to a unified lib+bin layout, where once you install loco you get both the library and binary of loco new

As part of that we'll also move to a similar-to-rails app starter generator, where we will compose a new app based on user's selection of options rather than clone and copy a starter.

related:

• reduce monorepo footprint #881