Horizontal datum - revised

[lavanya3k]

Description of the PR: This is a pull request for validating the presence of horizontal datum name. We make recommendation whenever the horizontal datum name is not present. The error message is revised as per the suggestions, and tested with sample record having a horizontal datum name.

Code change: Code changes are made in the rules_override.json and check_messages_override.json (ignore the changes in checks_override.json). Further, we updated the outdated files in the test_downloader.py and schema_validator.py. There was an outdated imports DraftValidator, and this has to be updated before every commit. The final code is test by running pytest, and the run was successful before committing the code changes.

To reproduce:
C1000000018-CDDIS --format umm-c
C1422070882-CDDIS --format umm-c
C1406820051-CDDIS --format umm-c
Test file: Create a test file with the following format
{
"SpatialExtent": { "HorizontalSpatialDomain": { "ResolutionAndCoordinateSystem": {"GeodeticModel": { "HorizontalDatumName": "WGS 84"}}}}
}

Expected output:

[lavanya3k]

Testing on the dev branch: The following concept IDs were tested, and they passed the checks.
C1000000010-CDDIS --format umm-c
C1000000023-CDDIS --format umm-c

[lavanya3k]

Expected outcome in the dev branch: