If there are many translations for an item, the number of buttons on the babel view
can be overwhelming. Therefore we add a configurable parameter (int) to limit the
number of buttons to be displayed. If there are more translations than this number,
a drop-down is used instead.
XXX Fixme: this changes requires re-installing PAM, or at least re-running the
"Control Panel" step in GS. Needs to be made non-intrusive
make max_nr_of_buttons also available in the babel view (for AT)
add backwards compatibilty: initialize the new control panel field with dummy
value, before attempting to save it
Merge pull request #37 from pysailor/babelview-dropdown

Babelview: use drop-down for languages instead of buttons when there are too many translations