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.
for the tests, the solution to some of the function is not unique or exact. for instance, 
```
In [1]: _sphere_to_cartesian(np.pi, np.pi, 1)
Out[1]: (1.0, -1.2246467991473532e-16, 1.2246467991473532e-16)

In [2]: _cartesian_to_sphere(1,0,0)
Out[2]: (0.0, 0.0, 1.0)
```