Split up large developments into phased subdivisions about developer

[pksohn]

This is really two big stories that we need to get specific about how to handle:

• Phased development - this is the idea that a development project can take longer than one year to complete.
• Split developments - this is the idea that beyond a certain square footage, a parcel is too large to be realistically treated as one potential building, and we should figure out a way to procedurally or manually split the parcel into multiple developable entities.

We have to decide at what "unit of development" these behaviors are handled. Some options off the top of my head:

• Stick with parcels. Split parcels into multiple parcels where need be.
• Replace parcels with something else, like "development sites" as the primary unit of feasibility/development analysis. Parcels can be split into development sites but most parcels are 1:1 with their development site.
• Something else?

This should be split into sub-stories once we have more specificity about what might work best.