Bug 33744: Fix cloning (sub)fields with framework plugins

Bug 33744: Fix cloning (sub)fields with framework plugins

This patch is meant as a temporary measure for fixing the problem.
Bug 30975 may resolve it further, but this is good for now.

Note: The original commit message referred to removing a deprecated internal
structure. But this patch actually still uses the structure which has been
moved to _data in jQuery now.

Test plan:
1) Apply patch
2) Repeat steps in the original bug description
3) This time clicking on the Upload button for a cloned field should launch the uploads pop up.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>