Install external packages

[kabilar]

• How should we install and/or document installation of external packages (kilosort, scanreader, caiman, etc.)?
• Each package is required for use in the respective Elements and Workflows.
• Packages often have unique installation instructions, and cannot always be included in the requirements.txt.
• For some packages, we have previously had the extras_require feature in element-interface.
• For some packages, installation is currently in the Workflow Docker files.
• We need a consistent strategy across all Elements and Workflows.
• Also, see Update Elements and Workflows once element-interface is published on PyPI #47

[CBroz1]

My suggestions would be motivated by (a) making installation easiest for the average user and (b) making all elements compatible with one another, and explicitly documenting any incompatibilities. I think this means

• Maximizing what is pip installable from PyPI
• Adding documentation to the specific element for how to install what remains (e.g., CaImAn)
• Removing hard pins in favor of <= or >= wherever possible
• Removing any need to refer to corresponding workflow repo