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.
Removed commented lines
make fit_sphere_to_headshape look for cardinal digitization points.

Currently, fit_sphere_to_headshape only takes digitazation points of
type 'extra' into account. It should first look for cardinal landmark
points and only if these are not found look for points of type 'extra'.
make `fit_sphere_into_headshape` work with both cardinal and extra points