Unspecified dates previously could not handle qualification. Unspecified dates also couldn't handle dates with 3 unspecified digits ("1XXX"). This commit adds both those features and tests for those use cases.

Requires quite a few overrides of lower_ and upper_ range methods to properly handle dates due to padding working in the opposite direction for negative dates, esp when combined with month/day padding.

If not in debug mode, use a simpler EDTFParseException rather than returning the full pyparsing error

Includes handling for empty or null input strings and null errs passed to the constructor

Co-Authored-By: aweakley <224316+aweakley@users.noreply.github.com>

Make the string representation of TestEvent simpler