During Debug : Enforce Document Level Ordering of Mutations

As of vulcan: if a user initiates a debugging session, then only one arbitrary mutation is taken and given to a worker for processing; the other mutations from the doc will be processed in other worker threads in the meantime, resulting in a completely out of order sequence. 

It is important that the user be able to debug in Production, and for it to happen it is important that the ordering be maintained.

Hence, it is recommended that, ordering be enforced at a document level always, and mutations to a given document are always processed in sequence.