Move Actions to use UUID instead of Sequence

For a couple different reasons Action identifiers (and therefore tags) are moving away from using integer sequences generated in state to using UUID's for the unique portion of the _id.

One reason is that sequences are misleading because they imply ordering that cannot be guaranteed.  Another reason is that a soon coming change will consolidate Actions and ActionResults into one type and the combined type will use a UUID as the _id rather than a munged prefix and suffix.  Yet another reason is that the Actions spec calls for UUID identifiers of the Actions on the command line.

Because of the consolidation of Actions and ActionResults, the ActionResultTag is also being removed from the names package.


It's used in production code, but it's vestigal from when we had two different kinds of Action Tags (Actions and ActionResults), and needed a way to smoothly convert between them.  This whole Prefix/Suffix bit will be removed in a soon coming iteration of the Actions/ActionResults refactor.