WIP it does something. not sure if it helps.  also doesn't support multi-processing.

This is a draft of how to support caching inference.
It is basically only for opengm, and only does something sensible for selected inference algorithms that can cope with ``init``. There are all the sampling and move-making based methods, I believe (try ``'lf', 'fm', 'icm'``).
I couldn't see much gain, but maybe there is still some bug.