Bug 7125: make MARC framework tag form not suggest that one can change the form

When you edit an existing tag in a MARC framework the form makes it
appear as if you can change the tag number when in fact you cannot. This
patch changes the template so that the tag number does not appear as an
editable form field during the edit process.

To test, apply the patch and open an existing MARC framework in
Adminstration -> MARC bibliographic framework.

- Choose an existing tag from the list and click 'Edit.'
- The line labeled "Tag" should display the tag as text.
- Making a change to any of the tag's details should work correctly.
- Return to the list of the MARC framework's tags.
- Click 'New tag.'
- The line labeled "Tag" should display a blank form field.
- Create a new tag and confirm that it saves correctly.

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as describes, on edit and new.
No koha-qa errors

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Work as described, template change only.
Checked editing and adding tags.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>