Add classic diffraction features

[erjank]

1. This may overlap with issue port over functionality of diffractometer from cme_utils #2 , but being able to click on a peak and know the length scale it corresponds to (a calculation involving simulation unit conversions, zoom, and the box length) will be super handy.
2. Also, the ability to write out a finished publication quality diffraction image with axes.
3. AAAAND! Check if rotations about the z-axis also rotate the diffraction pattern about the z-axis. Something about the diffraction pattern rotation seems a bit off looking at the lamellar example. It's not a huge deal, but having as close to 1-to-1 rotation correspondence would be nice.

[jennyfothergill]

3. The z-axis rotations is definitely a bug-- the rotation matrix currently doesn't take into account the up attribute of the camera, so I think fixing this issue could be as simple rotating the final diffraction pattern by the angle between [0,1,0] (default up) and current up.

[jennyfothergill]

2. Should be nearly resolved by the Figure example notebook and by the file menu option (save diffraction pattern). I just need to add axes that make sense, which might depend on 1.

[jennyfothergill]

1. This one is tricky if we want to think about "real units" because knowing what units a file is in is hard. If we just want to get these units in "simulation units", that should be pretty doable.

[jennyfothergill]

I am closing this with the intention of breaking it into atomic issues