Ferric `init` command

[kraenhansen]

To make it trivial to start working on a library using Ferric, we'd like a command to initialize a simple package.

It should work in two modes:

• Creating a new package structure.
• Modifying an existing package structure.

I imagine running the command would leave the package in a state, much like the ferric-example package and we might want to simply run the command to initialize the example on CI.

[kraenhansen]

An existing attempt was already started in #206