Bug 11611: Rephrase description and examples of 5 MARC related sysprefs

This patch rephrases the description or examples of 5 sysprefs:
1/ MARCAuthorityControlField008: "MARC" -> "MARC21"
2/ itemcallnumber: "Examples" -> "Examples (for MARC21 records)"
3/ DefaultLanguageField008: "Range 35-37" -> "Range 35-37 of MARC21 records"
4/ MARCOrgCode: "new MARC records" -> "new MARC21 records"
5/ UNIMARCAuthorityField100 description: "Do NOT include the date
   (position 00-05)." -> "position 08-35. Do NOT include the date
   (position 00-07)."

It also adds description in SQL systempreferences table for
UNIMARCAuthorityField100, MARCAuthorityControlField008 and MARCOrgCode.

Test plan:
- Apply and run updatedatabase.pl
- Check the changes are taken into account in syspref administration
  page
- Check the changes are taken into account in systempreferences table
  (for UNIMARCAuthorityField100, MARCAuthorityControlField008 and
   MARCOrgCode)

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Bug 11611: DBRev 3.15.00.017

Signed-off-by: Galen Charlton <gmc@esilibrary.com>