Bug 21225: Add Syndetics cover images to staff client.

Bug 21225: Add Syndetics cover images to staff client.

To test:
1 - Enable system preferences:
    SyndeticsEnabled
    SyndeticsCoverImages
    SyndeticsClientCode (you will need a valid code for testing)
2 - Perform a search on the staff client
3 - Check that results have images if upc,oclc number, or isbn existin record
4 - Confirm that dtails paeg displays same image
5 - Confirm size on details page follows syspref  SyndeticsCoverImageSize

Signed-off-by: Barbara Johnson <barbara.johnson@bedfordtx.gov>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>