Update serials docs for 2.4

In version 2.4, the serials modules underwent significant changes that
require significant updates to the documentation. This commit provides
the necessary updates, including some new screenshots. And in a few
cases, existing documentation was corrected or improved in ways
unrelated to the 2.4 update.

Signed-off-by: Remington Steed <rjs7@calvin.edu>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>