Feature: Limit webform submissions per object

[patdunlavey]

Add the following options to the webform configuration page's total submissions limit and per user submissions limit: "ever, per Islandora object" and "at a time, per Islandora object".

The purpose of this is to provide the option to restrict submissions of a given webform per islandora object; either total submissions or for the current user.

• "Ever..." means all submissions for this object. To permit new submissions, you would need to delete existing submissions.
• "At a time..." means submissions exist that have not been ingested. Once existing submissions for this object are either deleted or ingested, then new submissions are allowed.