Make components dir unconfigurable.

In these early stages, it's probably better to enforce a certain Figment
world directory structure than to make everything configurable. Until I
have more info on use cases, anyway.

I'm thinking something like this:

    my-world/
        components/
            __init__.py
            thingy.py
            whatever.py
        zones/
            default.json
        config.json
Add `figment new` command.

This copies a skeleton world structure into a new directory, making it
(hopefully) easier to get started. Kinda like django's startapp.