Core: how to deal with discarded peaks when reintegrating

During integration, many peaks will be marked as disabled for various reasons. However, they are not re-enabled prior to reintegration (i.e. clicking the "integrate peaks" button a second time), resulting in more and more disabled peaks the more times the peak collection is integrated. There should be a method of resetting a peak collection to its pre-integration stateso that results are valid after integrating a second time.