Bug 27416: Make "Modify tag" and "Add tag" translatable

Bug 27416: Make "Modify tag" and "Add tag" translatable

Those two strings are not translatable as they are passed from the
controller.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 4491cdd803226c22c585f3a23f6aa77000841bed)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 054428a57d4b810bc3278d625de573a66cb5d076)

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>