Consider use of Astropy QTable

Astropy QTables are Tables with units enforced in them. The databases I have worked with thus far don't have units stored in them, but it may be that some will (perhaps if the data is in long-form) or that it can be added via some map.
We may want to consider adding a `.qtable` method that will return query output but do so in QTable form. The simplest implementation would probably require the user to provide a dictionary of column -> unit, but we can explore other options too.