Add column 'attachments_allowed_p' to 'forums_forums', to be used to allow/disallow attachments on a per forum basis. Currently, the attachment logic is package instance wise, so if the forums instance has an attachment instance mounted below, then attachments are assumed to be enabled for all forums in that package instance. The idea with this change is to check for both the attachments instance mounted under a particular forum instance, and the 'attachments_allowed_p' column on 'forums_forums', to decide if attachments are enabled or not (both should be true). Next step would be to rewrite the logic to achieve that.
