Document how to use ipfx with NWB1 files

[wbwakeman]

The decision to drop support for NWB1 files in ipfx 1.0 is problematic for people that still want to use NWB1 files for cells in the Allen Cell Types database. ipfx should clearly document how to get a version that still has this capability.

As a computational neuroscientist, I want to know how to use ipfx to analyze cells in NWB1 format, so that I can analyze cells that are available from the Allen Cell Types database.

Add NWB1-supporting version of ipfx to Pypi, downloadable with NWB1Support tag

Acceptance criteria:

• [ ] Clear instructions are available in ipfx describing how to use an ipfx version that still supports NWB1 files
• [ ] Can download earlier version of ipfx with NWB1 support from Pypi

[wbwakeman]

Also consider informative messages that will appear on these pages: https://allensdk.readthedocs.io/en/latest/ https://allensdk.readthedocs.io/en/latest/cell_types.html#neurodata-without-borders

[tmchartrand]

are we not also making NWB2 versions of older Cell Types cells available through AllenSDK?