Fix EEG electrode positions in EDF/BDF import.

When importing EDF/BDF files, an optional .htps file can be supplied to
provide electrode coordinates. This commit fixes the way these are
stored in the .info dictionary, so that functions such as
make_eeg_layout can use them.
Sorry, I don't know what point_dict is used for. Do these describe what the electrode positions are to MNE? In that case I don't think the positions are actually landmarks, are they?