DecoratorView is a hack, replace with an Axis-aware grid view

[tuner]

... that can be specialized into vconcat, hconcat, concat, repeat, and facet (Vega-Lite style faceting, not samples faceting).

Background: Currently, DecoratorView wraps the actual view and handles its axes, view background, and zoom/pan interactions. However, it's difficult to use with faceting and shared axes, etc. Also, in case of facet, state of multiple decorator instances need to be tracked.

The new view could have responsibilities including but not limited to:

• View titles #28.
• Axes and Axis grid lines #58
• Annotations such as
  • the threshold of score-based semantic zoom
  • citations for the shown data
• Panning and zooming of scales that are shared between the child views
• Brushing
  • An example: We have multiple genomic tracks, all having a shared x scale and channel. The brush should span all the stacked tracks