Make ti possible that 2+ gadgets having same preference fields form work in ERP5 like one HTML form name space without conflicting each other (i.e. if two fields for 'field_my_title' exists they are transmitted as a list of two values, now no longer). Trick is to use unique form field prefixes for every gadget preference form.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@33683 20353a03-c40f-0410-a6d1-a30d3c3de9de