Misc Windows problems

[danielballan]

I walked my dad through this for his work and we found some issues on Windows:

• Conda on Windows does not seem to provide a python3 binary. One must type python instead. This would require a lot of "If on Windows..." additions to our documentation. I'm not sure yet how best to handle it. Maybe conda can fix this, but I bet they have a reason for not including it.
• The instructions for activating a venv environment use the . command which is not available on Windows. (We should probably strongly recommend Windows users use conda anyway.)