(fdo#78826) HIG: add missing colons in optformula

Also:
 * Use Unicode ellipsis
 * Shorten section heading (see fdo#84057)

Change-Id: I37cefa8a39c8907c7cbc138b255f2f8e78002c47
Reviewed-on: https://gerrit.libreoffice.org/11531
Reviewed-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>
Tested-by: Samuel Mehrbrodt <s.mehrbrodt@gmail.com>