make number of object wavefronts depend on object position

Instead of assuming the object is inside the diagram canvas
and setting the max radius of its circular wavefronts
to the worst possible such case
(when the objest is in one of the corners),
make this depend on the object position,
allowing the setting of objects' locations far away
(e.g. to simulate near-planar waves)
and skipping the drawing of waves that wouldn't be displayed anyway
(although probably canvas has a smart way of ignoring drawing instructions
when the pixel locations are off-canvas, so the latter may not be
as much of an improvement as the former)
minor tweaks
prepare code for normalization of cumulative hologram
normalize cumulative hologram (i.e. increase its contrast)
draw cumulative intensity curve