Run independent parameter sets in parallel

I implemented a preprocessor option for running multiple parameter sets in parallel. This feature leverages the Tempering infrastructure and omits MPI blocking between different parameter sets, which occured when calling subroutine make_truncation and the tempering exchange steps. Furtermore, with this option, VAR_HAM_NAME and VAR_QMC and not read from parameters, but from Temp_{igroup}/parameters.