This fix is the refactoring of the compare operation (issue #1886).
- CompareOperation is now an interface
- processing is implemented in
- CompareOperationBasis,
- LocalBackendCompareOperation
- LocalBackendWorkflowElement
As for the other operations, CompareOperationBasis is
wrapped by CompareOperationWrapper. I have also
created an OperationWrapper to implemement the
Operation interface so that other wrappers don't have
to implement the common interface defined by Operation.
OperationWrapper is intended to be subclassed by all the
wrappers.