Bug 19522: Label creator - some strings are not translatable

Bug 19522: Label creator - some strings are not translatable

Templates: new form:
Add hardcoded unit names to make them translatable.

Test plan:
1. install the fr_FR locale
2. go to /cgi-bin/koha/labels/label-edit-template.pl?op=new
3. then you should see the "Unités" dropdown with english units
4. apply this patch
5. install the language
6. refresh the page
7. then you should see the "Unités" dropdown with french units

Signed-off-by: Simon Pouchol <simon.pouchol@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>