Building a bunch of virtual envs later is going to be tedious if we do not
pre-cache certain annoying-to-build packages.
* tools/build_wheels.sh: pre-build some wheels for annoying package installs
* list distro package dependencies in files/*/venv
* list packages to pre-build as wheels in files/venv-requirements.txt
* install database Python modules when setting up the database
Change-Id: Idff1ea69a5ca12ba56098e664dbf6924fe6a2e47