Add functionality for 1) shape metrics; 2)polygon areas; 3) re-rasterizaton

[ldemaz]

This supersedes #2.

To add:

1. Functions for calculating shape metrics for polygons, to add as attributes;
2. Polygon area, including option to select appropriate CRS (default of ESRI:102022 should generally be adequate)
3. Rasterization of polygon ID, area, and shape attributes.

There is an argument to be made that these should be done as part of MakeInstances, but it is probably better to have it be standalone because we would rather have merging done first. Alternatively, 1 and 2 could be done right after merging as an option, and before parquet making. Rasterization can be standalone.