This PR introduces the cuts addon, a flow dissector that allows you to select
and operate on specific components of flows. It also adds the first consumer
for cuts - the cuts.save command.
Save the content of the focus to /tmp/foo:
cuts.save s.content|@focus /tmp/foo
Save the URL and response content-type headers for all flows currently shown to
file, comma-separated, one flow per line:
cuts.save s.url,q.header[content-type]|@focus /tmp/foo
We also use this to replace the body save shortcut in the console flowlist.