Fix various parsing errors

[MicahGale]

Pull Request Checklist for MontePy

Description

This fixes a few small syntax parsing errors. This fixed errors with parsing blank sdef by adding a rule for the parser that sdef uses to allow only a classifier. It also fixes an error with SSW. The issue is that the first word after the classifier was a keyword. There was a rule that allowed vol no 1 2 3 and this gets confused for ssw cel=1. So the solution was to not consider the no in vol no a keyword as it isn't part of a key value pair.

fixes #636, fixes #639

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📚 Documentation preview 📚: https://montepy--645.org.readthedocs.build/en/645/