Enable the simulate API to utilize modals

Currently when we use simulate, we use +/- instead of modals. We write p+(1, 2) to mean insert[p(1,2)]. We use p-(1,2) to mean delete[p(1,2)]. It would be nice if we could eliminate the +/- annotations and use modals instead.

Once modal-operators-2 is completed, we would be able to use modals to insert/delete rules as well.

We should keep the +/- notation as well for backwards compatibility, at least for a couple of cycles. Once the modal notation is ready, we need to be sure to mark the +/- notation as deprecated in the docs.