Interactive main timeline

[michaelbrooks]

The main timeline should be interactive. Participants wanted to be able to zoom in on a feature they saw in the main timeline without having to map it to the overview first.

Likely the easiest way to support that is by adding the zoom/pan d3 control to the main timeline. There is already an overlaying <g> element which could be made to receive the mouse events. The changed view interval would then need to be communicated to the overview timeline and the rest of the application somehow. It is possible that simply adjusting the interval model would work.