Add support for loading, creating, and displaying geomarks

Add a snapshot view icon to the map controls that creates a geomark out of the current mapview, assigns it a name (e.g. view yyyy-mm-dd hh:mm:ss ) and stores it in a Geomarks tab which contains a list of geomarks in most recently created order.

In the Geomarks tab, each geomark should have two controls: Zoom (search, display?) and Details. The Zoom control zooms the map to the geomark extent. The Details control hyperlinks to the geomark info page in a new browser tab. The hyperlink href is assigned the geomark url and the link text is assigned the view name (e.g., view 2017-04-22 12:03:57). The user can bookmark the geomark if they want to access it in the future.

The geomarks tab should also have an add geomark control that allows a user to load an existing geomark into the map.