make graphs zoomable

As number of dates increases, graphs are harder to read and appear mostly flat.
We want to be able to select an area of the graph and have a zoom in on this area.

Selection could be :

• directly on graph (click, hold and pan between bounding dates)
• through a range slider (adjust min/max dates sliders to enclose area of interest)
• entering min/max dates in editable text boxes (?)

Zoomed-in area should appear in new window or sub-window next to original graph.