Proposal: add event markers to history

[imaitland]

Perhaps just a vertical line.

Relates to #48

• Record abort events #196

[imaitland]

This ui task to overlay log data (exceptions, config updates, other events) with the history time series data.

[amitschang]

We got a request from Nate which I think might be nice to build in from the start:

Classify (e.g. draw with different colors/styles) the vertical lines by some property. At the moment we don't handle all extra data, but #220 should fix that. Then we can perhaps have a known property or enable selection of property to classify by.

[amitschang]

See ssec-jhu/evolver-ui#18 for initial version adding line in