Show the instance boundaries during the add process

During the "enable placing" phase of adding a map feature, we show the
instance boundaries are stop the marker from tracking the mouse once
outside the boundaries.

This gives a good visual indication of where to place things in the most
likely time for a plot to be added outside the instance boundaries
Add validation to prevent adding features outside the instance

 - The add tree process will return to the first step that had an error
 - For convenience, geom errors are returned as "mapFeature.geom"
 - On the plot detail, geom errors are at the top of the form

Fixes #1625
Merge pull request #1638 from maurizi/prevent-adding-outside-bounds

Prevent adding map features outside instance bounds