Unify filtering and validation logic

[andyward]

For some facets we have separate code paths for applying a filter to a model query (i.e. for querying/selection - typically used in applicability), and validating the elements (used by requirements). While there are reasons for the split (e.g. when verifying we want very detailed information on the failure reasons), we need to avoid subtle differences in implementations. As such we want to be re-using as much of the boolean logic as possible across selection and verification.

Generally speaking we want to be re-using the logic in Extensions helpers