[FEATURE] Allow copying from another language

This patch extends the "Copy from default elements" buttons by a dropdown
list of available languages. Clicking one of those languages creates
independent copies (not references!) of the selected language.

Resolves: #68395
Releases: master
Change-Id: I2ce443644ca1fbc6f0c41bc5917515b2784bc155
Reviewed-on: http://review.typo3.org/41768


Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>