Make sure the transaction note does not get too long.

Zope limits the transaction note length. By actively managing the transaction note we can provide fallbacks for when it gets too long because a lot of upgrade steps are installed at the same time.

@Tschanzt I've implemented a more complicated version of your fix in #39.
With this approach we can try to have as much information in the transaction note as possible, with a graceful fallback by first removing the upgrade step descriptions and if it is still to long cropping the note.