Option to attach even when view is empty (has no results)

In some use cases when the view attached to a node is empty, it may be helpful to display the view's empty text or even the altered footer of a view that contains a form to add a new item that would cause the attached view to not be empty (eg #1392768: question and answers (Q&A) feature & Origins theme tweaks which has an "Add new answer" form added below a list of answers to a question, whether or not answers have already been submitted).

The attached patch makes this an option on a per-view basis.