Collapse Kernel.TransactionImplementation into KernelTransactionImplementation.

o In order to make Transactor testable we have removed the MicroTransaction
   execution concern form KernelTransaction. To do this we had to expose some
   more schema operations from Statement.
Merge pull request #1235 from benbc/2.0-KernelTransaction-hierarchy-collapse

Collapse Kernel.TransactionImplementation into KernelTransactionImplemen...