Python exposure of JCFpmPhys AE attributes

JCFpmPhys: making some recent attributes hidden to Python. They are anyway not convertible at the moment.

This solves the current issue (before the changes in this MR):

In [1]: jphys = JCFpmPhys()
In [2]: jphys.dict()
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/home/jerome.duriez/Yade/install/bin/yadelevelSet in <module>()
----> 1 jphys.dict()

TypeError: No to_python (by-value) converter found for C++ type: std::vector<Interaction*, std::allocator<Interaction*> >

In [3]: jphys.clusterInts
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/home/jerome.duriez/Yade/install/bin/yadelevelSet in <module>()
----> 1 jphys.clusterInts

TypeError: No to_python (by-value) converter found for C++ type: std::vector<Interaction*, std::allocator<Interaction*> >

At least, it re enables the possibility asking for dict(). Obviously jphys.clusterInts (and others) is still impossible in Python, and that attribute is now missing in the online doc.

The MR is open for discussion before merging...