Bug 9545 - Fix import MARC bibliographic framework text label

Bug 9545 - Fix import MARC bibliographic framework text label

This patch improves the labeling of import controls on the
MARC frameworks page by making import options more explicit. Other
changes:

- Form markup fixed to match standard form constructions
- JavaScript corrected to make more embedded English strings
  translatable.
- Form labels made clickable by making "for" attributes match unique
  form field ids.
- Some warning re-worded for readability and translatability.
- Large "loading" icon replaced with more proportional smaller one.

To test, view the MARC frameworks page (admin/biblio_framework.pl) and
test Export and Import functionality. Clicking each should display a
form with options clearly labeled. Import and Export operations should
complete correctly.

Signed-off-by: David Cook <dcook@prosentient.com.au>
Works as described, although I see what Owen means about it being a good candidate for replacement with a modal dialog box in the future.

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>