Add icon with link to search results to open harvest calendar for that record

[thomasegense]

The record can be all mime types and not just HTML. Currently you have to hack the URL to show the calendar for a image.
In the calendar it would be good to also show revisits in another color. (revisits does not exists for HTML pages).

Task:
Backend:
Have calender method include revisits with a new revisit flag.

Frontend:
Add calendar link for each result in search list. This will also enable the solrwayback calender for users that only use PyWb as playback engine.
When reading the results, give revisits a new color.