Grante Wrapper

Since Grante requires c++11, for which OpenGM is not tested yet, the code is experimental.

To activate it You have to uncomment the option in CMakeLists, set the option to ON and change compiler options such that c++11 is used. This should work, but I will give no support so far. I guess there can be side-effects to other parts of opengm which does not hold the stricter c++11 standard.

We will make OpenGM conform with c++11 standard soon.