Classifiers for test_cases

[IgnoredAmbience]

We're not making use of metadata contained within test cases.

We have is_strict and is_negative in the test cases table, but no means of querying this.

We also don't keep metadata for the es5/6 id fields, nor the features set.

Test paths would also be useful as classifiers, it is currently possible to do this with the test_id field in current classifiers. But, it is not clearly evident from the classifier ui at present though.