Added `flatten=False` as a parameter to all array-fetching methods except LazyArrays, which turns JaggedArrays into regular Numpy arrays by ignoring the starts/stops.
For `outputtype=pandas.DataFrame`, the `flatten=True` case makes the DataFrame's index a `pandas.MultiIndex` with "entry" and "subentry" levels. Branches with different jagged structure can be mixed because `pandas.merge` aligns them appropriately.