Allow users to prevent the Distribute transform from being added to algorithms

-algorithm something[distribute=false] prevents the default DistributeTemplate
from being prepended to the transform part of "something"
Proper support for usign the same Stream transform more than once
Only display the Show2 window after project is called at least once

Rather than showing the (empty) window after init is called, wait until
actually told to display an image to show the window.
Give composite transform a default way to handle timevarying child transforms

Move TimeInvariantTransformWrapper to openbr_internal.h, add a default way
for composite transforms to handle const project calls when they have
time-varying child transforms.