Aliases in documentation

[paquiteau]

with the new PySAP cross-plugins documentation, there is a need to harmonized the type specified in docstrings.
This goes for the "Parameters" and "Returns" sections but also for the "See Also" which refer to related implementations.

• np.ndarray -> numpy.ndarray
• OperatorBase, FourierOperatorBase -> add full module path
• ReconstructorBase -> add full module path

I will add any other relevant changes to this issue.