Syndetics and Amazon bugfix enhancements

Syndetics and Amazon bugfix enhancements

This patch resolves a number of problems related to Enhanced Content:

1. Previously, there was no syspref for controlling whether or not to display
Amazon.com cover images apart from other content. This had the side effect
of preventing use of amazon.com content alongside use of another provider's
images. This patch introduces AmazonCoverImages and OPACAmazonCoverImages,
and changes the name of AmazonContent to AmazonEnabled.

So, for instance, you can now enable OPACAmazonSimilarItems yet utilize
SyndeticsCoverImages for displaying those similar items.

NOTE TO DOCUMENTATION TEAM: please update references to AmazonContent
and OPACAmazonContent to comply with the above.

2. Fixes some semantically incorrect uses of AmazonContent (now OPACAmazonEnabled)
on the OPAC side.

3. Resolves once and for all, the normalization of ISBN,UPC,EAN and OCLC numbers
for all enhanced content elements; These elements can be normalized using the
new functions in C4::Koha; I've replaced use of the various previously used
variables $xisbn,$norm_isbn,$clean_isbn, etc with $isbn, and the template
variable normalized_isbn.

We finally have a single, consistant place to retrieve normalize values for
these fields given a particular record.

4. Adds Syndetics attribution statements to display of all Syndetics content
'enhanced content provide by Syndetics' or 'Enhanced Description from Syndetics'

5. Adds an option to view the large cover image on the detail page on the OPAC
when using SyndeticsCoverImages; this option is controlled by a new system
preference: SyndeticsCoverImageSize which has two values: MC (medium) LC (large)

6. Adds UPC and OCLC numbers for Syndetics enhanced content queries especially
helpful for finding enhanced content for DVD and Music materials

7. Adds capability to display Syndetics images to opac-user for checkouts and overdues

8. Updates to systempreferences.sql, and updatedatabase.pl database revision 015

Signed-off-by: Galen Charlton <galen.charlton@liblime.com>