Print cosmological input before evaluating likelihood

[EBHolm]

Sometimes when a bad cosmology input crashes CLASS, it can be difficult to retrieve the exact input which gave the error. It would be nice to have a flag --print-cosmo for the run mode of MontePython which, when activated, printed the cosmologies before trying to evaluate the loglkl. Then, if one finds an error, one can simply look up where the error came from.