Add functionality to support multithreaded use of the transcation.

a) Add support for a pluggable policy inside the transaction manager to do reconsiliation at transaction commit, i.e. have all the other threads associated with the transaction completed/disassociated themselves from the transaction? Only one thread will be allowed to perform the commit.

b) Provide a simple policy that throws an Exception and forces a rollback if one thread tries to commit while another is still associated with the transaction. This doesn't include any distributed transaction support.

c) Make the connection manager threadsafe under multithreaded use of a transaction.

Make a Branch off 4.0.1 and work there.