Combined updates: get_canopyheight.sh, get_bareground.sh, modscag processing in dem_mask.py

[jmichellehu]

Ran into issues with fetching tile_list using get_modis_tile_list() so I hardcoded western conus tile_list. I didn't troubleshoot beyond confirming modis_dict contains 460 items, but something seems to be awry with locating intersecting geometries.

[dshean]

Thanks @jmichellehu . Can you provide more infromation on the issues for the modis tile list? We just need an index of the modis tiles, which I downloaded and stored as a dictionary here: https://github.com/dshean/demcoreg/blob/master/demcoreg/modis_grid.py. We could likely find a geojson for the modis grid index and read on the fly.

I'm not thrilled about hardcoding to CONUS tiles, as this tool currently works globally.