convert crmod-style configurations to a Nx4 array

        CRMod-style configurations merge A and B, and M and N, electrode
        numbers into one large integer each:

        .. math ::

            AB = A \cdot 10^4 + B

            MN = M \cdot 10^4 + N

        Parameters
        ----------
        configs: numpy.ndarray
            Nx2 array holding the configurations to convert

        Examples
        --------

        >>> import numpy as np
        >>> from reda.configs.configManager import ConfigManager
        >>> config = ConfigManager(nr_of_electrodes=5)
        >>> crmod_configs = np.array((
        ...     (10002, 40003),
        ...     (10010, 30004),
        ... ))
        >>> abmn = config._crmod_to_abmn(crmod_configs)
        >>> print(abmn)
        [[ 2  1  3  4]
         [10  1  4  3]]

def _crmod_to_abmn(self, configs):
        """convert crmod-style configurations to a Nx4 array

        CRMod-style configurations merge A and B, and M and N, electrode
        numbers into one large integer each:

        .. math ::

            AB = A \cdot 10^4 + B

            MN = M \cdot 10^4 + N

        Parameters
        ----------
        configs: numpy.ndarray
            Nx2 array holding the configurations to convert

        Examples
        --------

        >>> import numpy as np
        >>> from reda.configs.configManager import ConfigManager
        >>> config = ConfigManager(nr_of_electrodes=5)
        >>> crmod_configs = np.array((
        ...     (10002, 40003),
        ...     (10010, 30004),
        ... ))
        >>> abmn = config._crmod_to_abmn(crmod_configs)
        >>> print(abmn)
        [[ 2  1  3  4]
         [10  1  4  3]]

        """
        A = configs[:, 0] % 1e4
        B = np.floor(configs[:, 0] / 1e4).astype(int)
        M = configs[:, 1] % 1e4
        N = np.floor(configs[:, 1] / 1e4).astype(int)
        ABMN = np.hstack((A[:, np.newaxis], B[:, np.newaxis], M[:, np.newaxis],
                          N[:, np.newaxis])).astype(int)
        return ABMN