Start strong-docs API docs.

Add docs.json with strong-docs configuration.

Extract the example of `models.json` into docs/configuration.md.
Split the boot process into two steps

Split bootLoopBackApp into two steps:
 - compile
 - execute

Most of the changes are just shuffling the existing code around.

What has changed:

 - `loopback.autoAttach()` is called after `models/*` are required.
   The calls were made in the opposite order before this commit.