Add example key to field descriptor

[patcon]

Would this be a sensible thing to add. In Toronto, each dataset currently gets an accompanying README file in CSV format, and they like to give one or multiple examples for each field.

Might be nice if we could suppled a string or array.

Thoughts? And thanks!

[rufuspollock]

@patcon nice suggestion. Atm this could be something of a best-practice pattern - before we formalize it.

Also in the spirt of generalizing: this type of info is usually part of "data summary / data quality" information. We've talked about this sort of thing quite a bit over the years - it is common practice. I've just opened #364 for this (as it seems we don't have an explicit issue for it already)

[pwalsh]

hi @patcon and @rufuspollock - so maybe we close this issue?