Close All Open Orders DEX... Dispensers, Swaps?

[davestaxcp]

This post is to mainly bring this PR from Dan to the peoples (and infrastructure providers) attention:

CounterpartyXCP/counterparty-core#3273

• It overviews the idea to be able to cancel all DEX orders in a single tx.

• There are notes of also the case of a sweep of an address with open orders in which the original idea for that edge case "was you should be able to move all you open orders to a new address all together"

• While this applies to the Counterparty DEX, it would be very useful for all Dispensers on an address (at least closing them, not necessarily the sweep function), and even open orders with Atomic Swaps?

• other edge cases and testing is noted too