Bug 26007: Improve information on Link and Koha link in MARC subfield configuration

The Link and Koha link paragraphs had some false information that is corrected by this patch.

For example:

• Koha link has no influence on searching
• Link requires an index name, not a MARC field and subfield
• The warning for running misc/batchRebuildBiblioTables.pl belongs with Koha link, not Link

added 3 commits

• 96f64e3d...79e3e59e - 2 commits from branch koha-community:master
• c05b4209 - Bug 26007: Improve information on Link and Koha link in MARC subfield configuration

Compare with previous version

merged