[development] Deletion API hits core

[Steven Wittens]

> This sounds like a transaction... http://en.wikipedia.org/wiki/ 
> Database_transaction

Part of the reason I committed this patch is because, while it  
definitely solves some annoyances and adds useful hooks for contrib,  
it is also subtly the beginning of a transaction API. I think it will  
be interesting to see the kind of things modules do with it, and like  
Form API, it will possibly get refactored (Form API 2/3) as well as  
branch out to other areas (Node/profile rendering arrays).

Steven Wittens