• Added a new extension type for mime renderers, with the vega2-extension as a built-in example. Also overhauled the rendermime interfaces.
  #2488
  #2555
  #2595
• Finished JSON-schema based settings system, using client-side storage for now.
  #2411
• Overhauled the launcher design.
  #2506
  #2580
• Numerous bug fixes and style updates.