Release checklist updates.

Release checklist updates.

These reflect the fact that I'm increasingly preferring to make a
release-candidate build a few days in advance of the actual release,
and give the team time to do a bit of testing on it before putting it
up on the live website. Hence, I can't _quite_ fill in everything in
the website announcement ahead of time - the release date has to wait
until we know what it is, which means I need to have 'now fill in the
release date' as part of the go-live checklist.

Also, I've provided a better bob command for doing a release build
(putting it somewhere safe to begin with, rather than leaving it
precariously in my normal build directory). And while I'm here, I've
standardised all my placeholder version numbers to X.YZ; previously
half of them said 0.XX :-)