Populate HEALPix bitmaps and JSON outlines for ZTF tiles from a vector graphics representation of the ZTF field of view

[lpsinger]

I removed the preComputed_ZTF_pixel_indices_256.dat and preComputed_ZTF_pixel_indices_512.dat files when migrating from a private to a public repository because these files were too large to store effectively in Git.

For every field, we need both a HEALPix bitmap and a JSON outline. It will be most space-efficient to store a vector representation of the ZTF footprint for some fiducial pointing, probably in a GeoJSON format, and derive both the JSON outlines and the HEALPix bitmaps from that.

Once this has been resolved, we can revert #1.

[lpsinger]

Done a long time ago.