Form: 1) subrecords supports per row '_rowClass' definition. 2) Rollover for subrecords.

UsersManual/Index.rst: See 'Type: subrecord'. Some hints how to use '_rowClass' to mark rows individual.
AbstractBuildForm.php: implement in buildSubrecord() parsing of column '_rowClass'. Active roll-over by assigning class 'table-hover' to the class.
formEditor.sql: disabled form element records now 'text-muted' displayed.