Update fild.textbox.php to group by value

Original group was done by handle causing no real grouping because all handle are unique
Added value attribute to the output of grouped item

Signed-off-by: Pascal Piche <pascal@nitriques.com>
Merge pull request #23 from PascalPiche/master

Updated grouping algo to made reel grouping by value instead of handle causing not a real grouping behavior because all handle are unique