7310a: Improving list permissions: Changing Koha SQL structure

7310a: Improving list permissions: Changing Koha SQL structure

Modifying Koha structure for improving list permissions.
Adds new table virtualshelfshares for maintaining shared private lists.
Adds three columns to virtualshelves for permissions per list.
Adds column borrowernumber to virtualshelfcontents.

Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Feb 28, 2012: Added three FK constraints for QA (for owner/borrowernumber in virtualshelves, shelfcontents and shelfshares). Resolved syntax error with a comment. Tested the install.
Signed-off-by: Ian Walls <koha.sekjal@gmail.com>