pw: Add a quick-and-dirty tool to deal with patchwork

The patchwork instance on ozlabs.org can sometimes be under heavy load,
making it difficult to manage patches using the web interface. Add a
quick-and-dirty tool that can scrape the list of patches that need to be
triaged into a local TODO list using the Patchwork API (which seems to
be more reliable, even under load, than the web interface) and some
commands to apply patches (using b4) and update patch state.

Signed-off-by: Thierry Reding <treding@nvidia.com>