Split Offshore and Onshore Wind for Reeds (#27)

[MRossol]

Implementation of #27:

• Add offshore kwarg to ReedsClassifier which will pull out offshore (offshore=True) or onshore (offshore=False) or ignore (offshore=None)
• Add a split_offshore value to the config, if True it will run the CLI twice, once with offshore=True, and once with offshore=False

[MRossol]

@grantbuster do you mind reviewing this before I merge?

[grantbuster]

Some advice on a json loads issue that I ran into with the reV CLI's. Formatting dict strings for CLI's is so difficult... I've tried json.dumps() before but click had issues with the format. I left a comment with the best method I found.

[grantbuster]

FYI you might need to do something like i did in the link below. Basically if there is a stringified dict "{col: False}" you need to replace "False" with "false" and "None" with "null" for json loads to work properly.

https://github.com/NREL/reV/blob/38e19cf5278a425d239c0dd8f0cc34f25c87e45d/reV/supply_curve/cli_aggregation.py#L195-L200

[MRossol]

Converted this into a utility function here and added it to the reeds_cli
NREL/reV#108

[grantbuster]

Great