Feature Hard-Code netCDF Input Variable Units

[N1ckP3rsl3y]

• Hard-code the units each input variables within the file SW2_netCDF_output_variables.tsv
• This will eliminate the chance that the user will input an incorrect unit under the "SW2 Units" column
• See #408

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.52%. Comparing base (8670d87) to head (08ae94a).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## release/devel_v8.0.0 #410 +/- ## ===================================================== Coverage 72.52% 72.52% ===================================================== Files 20 20 Lines 6001 6001 ===================================================== Hits 4352 4352 Misses 1649 1649 ```

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