Minor tidying of about half a dozen words

The changes in this commit are best shown with `git diff --word-diff`
or `git patch --word-diff`. There are about half a dozen changes
of 1-2 words or a comma, the reasons should be obvious.

The sentence with "can not just" seems to be correct formally, but
"can not only" seems to me better to warn the reader that this
is a phrase of the form "can not only do X but can also do Y";
"can not just" sounds a bit like "You cannot just enter the room
without knocking" - it doesn't require a second part.

0 files changed, 0 insertions, 0 deletions