Sidebar configuration

[fschmenger]

This adds a sidebar configuration object to the application context, to customize some basic sidebar behavior - closes #217.

"sidebar": {
  "visible": true,
  "width": 400,
  "color": "white",
  "autoScroll": true,
  "scrollDuration": 500
}

A new sidebar scrolling feature has been implemented, to automatically scroll to the active module, typically after a new module becomes visible.
I also decided to rework the style of the sidebar toggle button to give it a bit nicer appearance.

The documentation has been updated accordingly.

[JakobMiksch]

Code looks fine and it works well.
Two minor note inline.
Otherwise ready to merge from my side.
thanks @fschmenger

[chrismayer]

LGTM, thanks @fschmenger. Will merge once the conflicts are resolved.

[fschmenger]

OK, only a minor conflict in the documentation, was easy enough to resolve.