Draft: Coupling with openfoam v1906

The FoamCoupling engine now spawns the openfoam solver internally. Therefore, the user can simply run Yade in the 'usual' way, and we can possibly interface with different OF versions with almost zero changes in the OF side. Some rewrite of the coupling, which uses a single module for serial & parallel Yade cases. (Basically from foamcpl merge request).. Unfortunately the case with a single yade process hangs :(