integrate planar wave into hologram
[phase diff demo] documentation / code cleanup
[phase diff demo] rearrange layout
[phase diff demo] add intensity curves
[phase diff demo] unify coordinate system between hologram and diagram
[phase diff demo] make each intensity curve a different color
[phase diff demo] also colorize the actual ref and obj waves, to match the intensity profiles
[phase diff demo] make display of intensity curves optional
[phase diff demo] display intensity curves in a separate canvas
[phase diff demo] display master intensity curve