Reorder methods alphabetically.
Renamed temp variable.
Add more documentation.
Add/move #registered and registered? to public, also;

- Return the buffer name which was added.
- Add more documentation.
Add placeholder test cases.
Add API.render method;

Rather than queueing views up to be rendered, then triggering the respective refresh event, one can now render a view directly and it will be rendered immediately. If the rendering is part of an event with throttling or debouncing, this is also honoured.
Make #registered? a public method.
Add tests for Common.
Add Registrar class to record new interface definitions;

This class also stores the associated Buffers, Focus, Groups and Interfaces repositories, and the Refresh events for the new interface.

- Remove #create from Buffers.
Minor refactor for #processed_lines method.
Add functionality to return defined menus.
Move the creation of refresh events into Interfaces and Groups.
Add more documentation.
Add an attributes test for Common.