(sort invocation): Mention -k earlier, so

(sort invocation): Mention -k earlier, so
that the options are in alphabetical order.  Describe how -b works
more-accurately; this involves fixing some examples, too.  Mention
what happens if the start field falls after an end field or after
a line end.  Warn about using -k without -b, -g, -M, -n, or -t.
Add an example of how to sort IPv4 addresses and Apache Common
Log Format dates.  Remove a duplicate example.
(Putting the tools together): Use separate options rather
than agglomerating them.