Make sketch the default diagram theme?

[bollwyvl]

Elevator Pitch

After #40 lands (or during the process), change the default ui theme from min to sketch.

Motivation

min	sketch

Pro:

• The default UI is much less cluttered, probably ~20% more canvas visible
• A number of key features are put in more discoverable places than deep submenus
  • full screen
  • freehand drawing
  • templates

Meh:

• Shapes/Format are the same

Con:

These might be for lack of my looking, but that's a strong indicator of someone not being able to find something

• the Pages view is absent
  • but generally, multi-page views don't work as well in the various static exports, e.g. SVG, PNG
• the layout view is absent
  • hopefully, there's a way to get this back!
• some navigation is kinda broken, and haven't found ways to bring back layers, etc.
  • pan is activated with Alt+drag though have only tested on a trackpad... seems reasonable, especially if we had a tour...

Design Ideas

Not much to change!

[bollwyvl]

In view of #48, potentially reconsider reverting this change in 1.1.1

[bollwyvl]

Closed in #51, restoring min