* Add :sort filter run prefix, docs and tests. Also extended .utils.makeCompareFunction with a flag for caseSensitivity.
* Documentation updates
* Move case sensitivity handling entirely to utils method so it is reusable
Fixes#5246. Now the reduce operator and :reduce filter run prefix will
both return empty output when their input is empty, so that both can be
chained together with the else operator or :else prefix.
