Bug 22774: (QA follow-up) Add syspref descriptions to database update and sysprefs.sql

Bug 22774: (QA follow-up) Add syspref descriptions to database update and sysprefs.sql

Moves the updatedatabase entry to the new format and
adds information for the explanation column of the
systempreferences table.

Also slightly rephrases the description in the system preference
editor.

To test:
- Verify database update still works the same with addition
  of explanations
- Verify the sys pref description makes sense

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>