Ability to add attachments to a page without sending notifications to watchers

Users need the ability to add attachments without Watchers being sent e-mails for each one - something like the "minor change" checkbox that is available in the Edit Page function.

Issue Conf-2219 currently scheduled for 2.7, enables adding attachments at the time a page is created. However, the parallel situation often occurs when a page is edited or when a sequence of attachments is being added. The person adding the attachments should get to choose whether the addition is significant enough (or distinct enough) for a separate e-mail to go out.