Add support for <cinder type-list> and <cinder create --volume-type>

Added support for volume types
I understand this is implementing a singleton-like pattern... what I'm saying is that there's no need. setup_routes() in `jumpgate/volume/drivers/sl/__init__.py` is called exactly once when standing up each app instance, which will serve many requests. Anything executed there is safe to be assumed to be ran once... making the singleton pattern un-necessary.

**The goal**
I want to run this code once because it loads and parses in a file, which would be really expensive to do every request

**Singleton solution**
Load this into a global place and make logic that only loads this once. Testing this requires knowledge of how this object works and that it has already been loaded.

**My suggested solution**
Just load the file once and give it to the resources that need it. To test these functions, pass in what the resource needs explicitly.