Move to a non-blocking model for StreamTransform

Rather than having threads at each stage block, and wait for input, use the
global thread pool to only execute stages when they have input.
Tweaks to Show2, allow display of properties in the window title

Also, add FPSCalc, and FPSSynch to calculate the frequency of frames passing
through a stream, and to slow down processing to a specific frame rate (note:
does not work particularly well), respecively.
Merge pull request #33 from biometrics/dont_block

Update multi-threading model used by stream, and some gui tweaks