Easier method to order cart execution

[bsanders]

First, ordering carts is already possible and documented. See https://github.com/StackIQ/stacki/wiki/Setting-Cart-Order

Carts get enumerated according to the alphabetical sorting of the cart names.

To modify this order you must modify the order/edge tags in graph.xml files

It would be good to have an easier method to force an ordering. Perhaps a column in the database with an integer or something and some plumbing to set it.

[gregorybruno]

Each cart has a "provides" and "requires" fields.

If ordered, an entire cart runs before an entire other cart.

# stack add cart newcart requires="oldcart"