MCMC samplers tuning parameters for the short chain in calibration step

[salleuska]

Every short replicate chain, in principle, will re-tune step sizes and proposal covariances from
scratch. They should start from what the long observed-data chain settled on.

To do:

• Check Daniel's code at https://danielturek.github.io/public/saveMCMCstate/saveMCMCstate.html