Incomplete draft SPASE metadata for SWE level 3

[jtniehof]

Change Summary

This is a WIP draft of the SPASE metadata for the SWE level 3 product. @hi1011 will finish up and open another PR, but we are setting this up for early review of the format.

Overview

Add DICT_KEY for Parameter metadata; start a new file (and directory) for dataset-level SPASE metadata.

New Dependencies

None

New Files

• cdf/dataset_spase/imap_swe_l3.spase
  • Per-dataset SPASE metadata for SWE L3. This is a new directory; seemed to be the right location (parallel to the ISTP YAML files in config and the variable definitions in data_product_definition_csv)

Deleted Files

None

Updated Files

• cdf/config/imap_swe_l3_variable_attrs.yaml
  • Add DICT_KEY attribute for several variables to capture the SPASE metadata

Testing

None, YOLO