Add a method to dataset/query to append a group of OR conditions to an e...

...xisting where clause, and added a small set of tests for it.

Changes
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Added the andGroupedOr method to the dataset query object to allow adding a group of OR conditions to an existing where clause. For example ... AND ((x = 1) OR (x = 2)).

- [ ] @achura
- [ ] @aheuermann
- [ ] @andymoon
- [ ] @doug-martin
- [ ] @jvanwinkle