Bug 10357: Adding link for email notification for new subscription issues to opac...

Bug 10357: Adding link for email notification for new subscription issues to opac-detail

This patch adds the link to the opac-detail.pl page so it is less hard
to find.
Update: Fixing link to look like button, adding span ID around element
Update: Changing ID to Class
Update: Comment 14 fixes

To test:
1) Add a subscription, attach it to a record and select a notice under
'Patron notification'. Hit Next, fill in some fields and save the
subscription
2) Go to that record detail page in the OPAC. Go to the subscriptions
tab, click 'More details'. Notice how many clicks it takes to see the
'Subscribe' button
3) Apply patch and go back to the details page for the record
4) Notice now there is a 'subscribe' button
5) Confirm this button works as expected and you are redirected to
the detail page
6) Confirm 'Cancel' works and redirect works too
7) Go down to 'More details' and confirm the buttons work and you are
redirected back to the serial-issues plage from here

Sponsored-by: Catalyst IT
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Signed-off-by: Séverine QUEUNE <severine.queune@bulac.fr>
Followed test plan, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Re-tested, works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>