Bug 18789: Use Koha::Patron->image from the templates

Bug 18789: Use Koha::Patron->image from the templates

Now that we have the 'patron' variable in all our templates, we can call
Koha::Patron->image and do the check from the templates.

Test plan:
On the different pages of the patron module, you should see the default
image if there is no image attached or the one that has been attached
(see pref patronimages)

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>