fixes for wfrc
Merge branch 'master' into fixes-for-wfrc
sometimes there are vacant units for buildings that don't make it out of the merge

basically the building DOES exist, but when it's merged to nodes, some of the node_ids are missing because there are parcel_ids in the building table that don't exist in the parcels.index.

anyway, at this point we deal with the issue appropriately and print a warning so this shouldn't come up again.
Merge pull request #4 from synthicity/fixes-for-wfrc

This fixes a few boundary cases that came up when developing the model for WFRC and at least one bug that came up when buildings were referring to parcels that didn't exist