Minor fix to as_dict and from_dict in StructureMatcher

[lbluque]

Summary

Include a summary of major changes in bullet points:

• Saves missing attributes in StructureMatcher.as_dict so that StuctureMatcher.from_dict can faithfully recreate the original object.

Checklist

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• Tests have been added for any new functionality or bug fixes.
• All existing tests pass.

[shyuep]

Thanks.