Integrate Dask Arrays properly

We can't currently go from DataFrames to arrays, #445 adds ``to_dask_array`` but this is only a bandaid for now.

I think in an ideal world we have an Array Collection that captures something like ``.values``, then you can do array computations and go back to a DataFrame collection. Downside is that an Array collection without methods is not very helpful

I am not planning on working on this immediately, but wanted to collect thoughts on this topic

cc @mrocklin @rjzamora

Start by reading the discussion on #446 and the related #445 change involving `to_dask_array`; no files, tests, or entry points are named. Before implementation, establish the intended Array Collection scope and its DataFrame conversion behavior, since the issue currently describes an open design discussion rather than a defined completion criterion.

Written by the indexing model from the issue text.