Implement updateConstraint and solveVelocityConstraint in pbdConstraint

    ///
    /// \brief update constraint
    /// \param model \class PbdModel
    /// \return true if succeeded
    /// TODO: Remove this or implement for child classes in future
    ///
    virtual bool updateConstraint(PbdModel& model)
    {
        return true;
    }

    ///
    /// \brief compute delta velocity, specifically for rigid bodies
    /// \param model \class PbdModel
    /// \return true if succeeded
    /// TODO: Remove this or implement for child classes in future
    ///
    virtual bool solveVelocityConstraint(PbdModel& model)
    {
        return true;
    }