Prepare moving KKRhost/torque.F90 to common.

@dias: Eduardo suggested that I should probably mention this to you, as this is basically your code. When we first discussed implementing the things from `bfield.f90` and `torque.f90` in KKRnano, we planned to use the modules from the common directory and not make new separate copies for it. For this reason, I moved the torque module from KKRhost to common and removed the explicit dependencies. This was dismissed later on because there are more differences we did not consider at first. But these changes were already merged, so if you don't see problems with it we can probably leave it.