Moves relationship access out of the LegacyKernelOperations.

 o Still delegates to old implementation, but this is now done through the correct call paths.
 o Locking has been moved to the Kernel locking layer.
 o Obviates the need for NodeLookup#lookup(), which has thus been removed.
 o Obviates the need for the lock that could be passed to getNodeForProxy, which has been removed.
 o Deleted relationships are now filtered out in StateHandlingStatementOperations.
 o Use primitive iterator on the low levels for rels