Bug 14424: Update Discharge Help for 3.20

Bug 14424: Update Discharge Help for 3.20

This patch adds the missing discharge help file and updates the moremember file with
info on discharges.

To test:

* Visit a patron
* View and confirm help is right
* Visit the discharge page on the patron
* Confirm help file loads and is right

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@koha-community.org>
Signed-off-by: Tomas Cohen Arazi <tomascohen@unc.edu.ar>
(cherry picked from commit a350d02b995483bdd3bc7ede2271ad8a17190acc)
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>