followup previous commit: forgot to commit the javascript as well
add support for animation
Fix phase control

plane wave phase change should affect hologram and intensity curve
like spherical wave phase change does now
allow dynamic adding and removal of object points
prevent multiple schedulings of refresh()

If refresh() is called while animate=true,
it sets up a setTimeout that is interlaced with the original one
thus doubling the animation speed.
make intensity calculation of planar wave more intuitive and more efficient
MAJOR: implement cumulative (final) hologram
code cleanup, organization & documentation