Bug 15851: Only display the analytics link when required

Bug 15851: Only display the analytics link when required

This patch makes opac-detail.pl query for analytics the same way it
would do with the generated link (i.e. based on UseControlNumber) and
passes a flag to the XSLT so it displays (or not) the 'Analytics' link.

To test:
1. Apply the first patch
2. Have a known record without analytics
3. Open the record in the OPAC
=> FAIL: It shows the 'Analytics' link
4. Have a record known to have analytics and open in OPAC, on a separate
   tab
=> SUCCESS: It shows the 'Analytics' link
5. Apply this patch and restart_all
6. Reload the tabs
=> SUCCESS: It shows the link where it has to, and hides it where it
shouldn't be displayed
7. Sign off :-D

Sponsored-by: Orex Digital
Signed-off-by: Hugo Agud <hagud@orex.es>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>