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.
@t3on please check whether you need unit information here, a.k.a 'cal'. The fiff i.o will store the data in 32 bits. If you don't calibrate e.g. 1e-6 if data in volts you loose precision.