Refine concave hull handling in forked forge-py code - for flight lines

[juliacollins]

Fine-tune the spatial footprint handling in forge-py for different use cases to ensure we're "close enough" to current MetGen output.

Relevant repository is https://github.com/nsidc/forge-py, branch is granule-metgen-investigation

[eigenbeam]

@juliacollins I've cleaned up my experimentation and simplified it down to couple simple operations. If you now specify the 'strategy' as 'concave' it will generate the flightline that I sent in Slack. See branch: https://github.com/nsidc/forge-py/tree/duck-issue-14

You can run this by:
$ python ./podaac/forge_py/cli.py --granule_config ./samples/irmcr2_20191109_01.concave.cfg --spatial ./samples/IRMCR2_20191109_01.csv.spatial --output_file geojson.json --config configs/config.yml

[lisakaser]

I am moving this out of sprint 3 as other issues have higher priority for MVP