Add ability to create new building plan from geojson file

[DavidGoldwasser]

I think the best way for this to work is for the user to choose a geojson file (uploaded one of possible, but could be link to URL). Then an additional use input would be the specific feature to import. The imported feature would result in a single space the shape and location of the building. The modeler can then slice that up into multiple spaces and then multiple stories.