Factor out geospatial meta-data extraction into a single extractor that downstream code will depend on

[dlebauer]

Description

The step(s) of converting from the lemnatec-provided metadata to a (to be determined) common reference system currently appears to be done in many different algorithms.

Once we do have a canonical set of reference points (terraref/reference-data#32) on the field scanner field, having only one place that does the conversion will make this easier.

TODO

• create the geospatial extractor ( Store location and field of view metadata associated with each file in Clowder #101) that stores geospatial metadata in Clowder
• Identify code that contains duplicated logic, make sure the best bits are in the geospatial extractor above
• Then refactor existing code to use data from the Clowder PostGIS database.

[max-zilla]

This is going into the terrautils library:
https://github.com/terraref/terrautils

I've already done synthesis of existing geospatial code into one place - last remaining issue is to get plot definitons from BETY as discussed here:
#307

Will close this issue so that issue can reflect last remaining task.