convert and test the Morphologist pipeline

[denisri]

One of the major goals for us is to obtain a new Morphologist pipeline in Capsul v3 structure, which is able to run.
The Axon->capsul conversion script has been reworked, and I think the converted pipeline has the correct structure and state. It has been added in morphologist-gpl in the capsul3 branch (as morphologist.capsul.morphologist).
I have not tried to run it yet because we need to implement the completion, and have the new execution infrastructure.

In addition, a FakeMorphologist has been derived from it, and set in capsul.pipeline.test.fake_morphologist.morphologist.Morphologist. Its structure and state is now (I think) the exact same as the original one, and it has no execution dependencies: it runs without the real morphologist software, and produces fake outputs just to test the pipeline structure.

We should build a use case to test it.