Build/test some minimal, non-full-Lab examples

[bollwyvl]

Elevator Pitch

A la jupyterlab/jupyterlab it would be useful to show how the existing/to-be pieces could be used without the full lab environment.

Motivation

To help move towards #76, this would help determine what parts of a full Lab are absolutely required, and potentially break up future packages according to their heavyweight dependencies. This would also motivate things that we can move into the editor itself, rather than building new fancy UI in new panels.

Design Ideas

• just an editor (no dockpanel)
• just a notebook (no dockpanel)
• minimal multi-editor dockpanel (with file tree, diagnostic panel)
• console (once we support console)

I think any more than that, and you've basically got a full lab.