expand
update
update
remove what should be dead code

While old propellor's can emit Ready, they won't if they've managed to
updateFirst. If updateFirst fails due to eg, inaccessiable central repo,
those old propellor's are not able to receive inline git pushes anyway,
so are not going to update no matter what, so no point in making --spin
work in that case.
add --update, which will one day replace --boot

But no time soon, since that would break --spin to old versions of
propellor

Maybe after 1 year?
reorg
fix long line
reorger to match usage
refactor
refactor
propellor spin