Convention-based project layout & a bootstrapper

[bajtos]

We should prescribe a convention for organizing different kinds of files in LoopBack-Next projects:

• controllers
• sequence actions
• models and repositories
• value providers
• etc.

There should be an optional bootstrapper that people can use to setup their application at runtime with as little code as possible. (I.e. an equivalent of loopback-boot.)

[bajtos]

Closing as a duplicate of #441