docs: a bunch of updates to simplify the process of installing from source and running Tahoe
These changes are a work-in-progress -- there are many incomplete and incorrect parts, but the install.html and running.html files
are complete and should work (and they are delightfully concise!). I'm pushing this just to let people see incremental progress
and to solicit feedback. "Testing out" the install.html and running.html files and submitting patches or bug reports would be
quite welcome.