Possible changes to treemap/management/commands

[ghost]

It appears that commands update_aggregates.py and testimports.py should be changed by removing the OpenTreeMap namespace from the lines 'from OpenTreeMap.treemap.models import Tree, Plot' and 'from OpenTreeMap.treemap import models' as was done earlier with resave_trees.py.
It also appears that build_exports.py is out-of-date (it references UrbanForestMap for instance) and unnecessary, and should be deleted.
I haven't tried submitting a pull request on this because I'm not sure of the project development intent - these files may be changed in the course of your current importer development.