Code debt payment

See previous MTC releases here - for now doing releases on UDST.

This release contains all the fixes from #84, which was a cleanup and code debt iteration. I will be merging and releasing the UAL code soon.

accounts implemented and merged

This is a good point to run the model system and requirements.txt should be in sync. This has a working version of residential development out to about 15 years or so, with supply and demand interactions and an example of subsidizing MF development in PDAs by taxing commercial properties.