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.
I think it would be awesome to have a Mixin in channels.py that does these more general kinds of things. I would put the code you have written to channels somewhere, maybe as read_fiducials / set_fiducials. The Mixin would then internally use them / that.