Add ability to select a single point on the map

[corviday]

Currently, the PCEX map allows you to draw a shape to select the area of interest, from which data is displayed. We want to display some streamflow data, where the area of interest is typically single point. The backend already supports returning data from a WKT point, so we should just be able to add a point selection tool to the map.

[jameshiebert]

There has been interest in adding the point selection tool to be available in all of the maps. Re-opening this issue to track that.