update: small improvements from devel_MPI and updated SciFor

update: added Broyden mixing in BHZ.
this is still under development, use with caution.
lines are commented, now.

update: BHZ-AFM driver updated with A(k,w) evaluation.

update: added analytic gradient for the chi^2 fit also in the
Superconducting channel for cg_scheme=delta. Test for Bethe lattice
successful.