Bug 34979: Fix mistakes in system preference files highlighted by unit test

Bug 34979: Fix mistakes in system preference files highlighted by unit test

This fixes the mistakes the unit test helped to find:
* Add missing system preferences to sysprefs.sql
* Correct spelling for AutoUpdateSetsEmbedItemData
* Correct capitalization, so that code and pref files match
* Fix OverDrive sytem preferences, where explanation/options
  columns where switched, resulting in strange database entries

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Victor Grousset/tuxayo <victor@tuxayo.net>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>