Improvements to maps:
* Improved colors for area maps (but still need to get rid of white end)
* Save and restore maps including legend, center, and zoom
* Use L.esri to get backgrounds from ArcGIS
* Improved the way changes in map layer are handled by MapView
* Attribute menu for map legends now shows and works
Merge branch 'master' of https://github.com/concord-consortium/codap
The colors in a map no longer go to white at the minimum. We have introduced a 0.1 offset by setting a new property in AttributePlacementDescription that is used in the computation of minMax.
Undoing inadvertent commit of commented out iframe-phone
* Fixed calculation of categorical colors broken by previous commit
* For continuous legend, justified the min and max numbers so they stay within view
* Fixed point data tips to show the first time (by getting rid of dependence on binding)
Merge branch 'master' of https://github.com/concord-consortium/codap