Reports access fields that might not exist for all AbstractTestSet types

[ssfrr]

here and here this assumes that you can get ts.results and ts.description for ts::AbstractTestSet, which won't in general be true. Perhaps we should add results(::AbstractTestSet) and description(::AbstractTestSet) functions to the AbstractTestSet interface (or maybe description could use some kind of string/show method or something.

[oxinabox]

You're right. I was thinking the same thing as I was writing it.
Should that be a method here, or should I escalate it to Base ?

[ssfrr]

I think it should be in Base, and then extended for other testset types (for instance I'd add a method for my ExtendedTestSet).

[mmiller-max]

To fix this, we need abstract methods that both set and access the results and description fields.