* \param[in,out] v Velocities will be stored when *v!=NULL
* \param[out] box Box dimensions
* \param[in] requireMasses Require masses to be present, either from tpr or from the mass
* \param[in,out] v Velocities will be stored when *v!=NULL
* \param[out] box Box dimensions
* \param[in] requireMasses Require masses to be present, either from tpr or from the mass