jQuery adapter doesn't support 'form' property

[heruan]

The jQuery adapter gets the form owner of an editor target element using $element.parents('form'); this is wrong, since a form element can be placed outside the form and associated with the form attribute (see ​http://www.w3.org/TR/html5/association-of-controls-and-forms.html). The jQuery adapter should use the form property of the form element which is its actual form owner.

[pjasiun]

in branch/ticket #10281