Bootstrapping project for new users

[flyinghermit]

What

Add a new command that would bootstrap a minimal project skeleton, and if necessary, perform actions such as authentication, create role templates etc.
The command would be invoked as $ predicate new "predicate_project_name"

Why

A basic project skeleton eases getting started with predicate.

[vitorenesduarte]

I would be cool to add a --import-roles-as-policies flag that would take the output of tctl get roles and translate each role to a predicate policy.