Minor fixes

Hey,
I've put two patches in this branch that I had in the pipeline for the next release. I've discovered that the signal scaler eats up a large percentage of CPU cycles in the current implementation while determining the maximum value in a stream of I/Q samples. This causes long delays, especially if the data stream is large. This patch adds a parameter to limit the number of samples the scaler uses to look for the maximum value.

The second commit is a simple helper script to setup up Tun/Tap devices on Unix systems.

Thanks
Andre