Allow use of monitors2 and thin2?

[salleuska]

Although they can be specified by writing a custom configuration, samples in mvSamples2 won't be returned to the final output. Should we make this possible to use? They may be useful to assess convergence of a set of nodes that are part of the model but of interest in the comparison.

[perrydv]

I think this would require a fair bit of effort and not be very generic to other systems. I suggest let's not pursue this for the initial version.