Modify C++ Faust::Palm4MSA, Faust::HierarchicalFact and Faust::ParamsPalm, Faust::Params to allow setting norm2 threshold and max iter arbitrarily (default values changed faust_constant.h.in).

In faust_constant.h.in:
- Change default parameters from 1e-4 to 1e-6 precision (used among other things for spectral norm).
- Rename spectral norm default parameter for max number of iterations to FAUST_NORM2_MAX_ITER.

Minor changes (display related) in test_palm4MSA.cpp.in and hierarchicalFactorization.cpp.in.