make activity graph interactive

[Gregory Smith]

Add the ability to navigate to specific workouts by clicking on the associated bar in the workout activity graph.

Also, extend the date range so that more workouts are shown (as shown in attached picture).

I believe that this can be done using the “tap” selection tool in bokeh. It also appears possible to use HTML links in callouts as shown here: https://bokeh.pydata.org/en/latest/docs/user_guide/tools.html#custom-tooltip

I found a specific example here: http://bokeh.pydata.org/en/latest/docs/user_guide/interaction/callbacks.html#openurl

[Sander Roosendaal]

fixed