Add Inquiry Response types and code to validate against the SDI spec

[AEgbert]

Brief summary of changes:

• Adds sample response (and changes request sample's file type to .json)
• Adds dataclass based implementations of the various response classes
  • Can instantiate from dictionaries with ResponseClass(**json_dict)
  • If contained objects cannot be converted from dictionary form, they will be included as-is without conversion. However, top-level objects must have only the expected fields.
  • String representation is designed to generate in a format similar to a formatted .json file, but with simpler syntax
• Pulls FrequencyRange out from request packet code into common section
• Adds validator classes
  • Can log problems to file, use standard logging system, and print to console
  • Attempts to report multiple errors (i.e., doesn't stop after the first error is encountered)
  • Only checks that a response meets the SDI spec--does NOT check for correctness or compare to expected response

I've tested the validator against a number of weird edge cases, but I can't guarantee I haven't missed something. Let me know if you have any feedback or specific validation edge cases you have concerns about.

[AEgbert]

I've corrected an error in the validation logic for the FrequencyRange class (commit). While not specifically stated in the SDI spec, it appears that lowFrequency should be strictly less than highFrequency, with each range being interpreted as [lowFrequency, highFrequency) (that is, lowFrequency up to but not including highFrequency). In discussions with @w4je, this may differ from the original intent of the spec, but other interpretations (i.e., up to but not including highFrequency+1) lead to ambiguous limits in interpreting the SDI spec's example response.

[AEgbert]

I believe I'm out of final tweaks to the code in this PR. If you'd like a shortcut to comparing the new code in this PR to the current branch, check here.

[AEgbert]

Rebased branch to include corrections from #8