#1493 fixes bug that deletes multipicklist fields when included in mass edit. Fixes bugs in automatic inclussion of fields for mass edit (checking the checkbox next to the field), as reference fields and multipicklists were not working.

fix for #1493. Avoids deleting checkbox and reference fields in mass edit. Since checkboxes and reference fields have hidden inputs in edit view, those were inadvertenly added in the mass save request.

fix #1349 and #1241 by adding deletion funcionality to mass edition. It adds checkboxes for each field in the mass edit layout, which allows delete fields by just checking the checkbox without modifying the field contents.