Tb montage enh

Adds montage option to edf and brainvision modules to provide standard import of electrode points.
Adds fiducials to the montage.
Organization of transformation functions into the transformation module.
@wmvanvliet are there any other cases you could think of where one would apply the fiducial transforms when applying a montage? I'm wondering whether it's only me who's struggling with this. The point is that a montage to me is about standard electrode positions. If you have polhemus you would have dig points and this is where they belong. If you have standard positions you won't really need fiducials, right? If we had a more generic function or method like ```.set_electrode_positions(montage='file.elp' | Montage('file.elp') | np.ndarray, fiducials='file.elp' | 'auto' | dict)``` it would be easier for me to buy.