Cleanup & api-ise the dedupe code

I've been looking at the dedupe code a lot. The problem is it was written to support a particular form & there is no layering. I think the right steps to clean it up involve adding some apis. I have been experimenting with a new angular interface but we need to expose the logic via the api for it to be usable. Currently I'm looking at adding find apis - looking at creating a new api entity 'Dedupe' (I could use 'Rule' and add actions - on the fence there)

& looking at an action Dedupe.getmatches