New DSP AnalysisLib class: peakamp

[lossius]

This would work in a similar way to the MSP peakamp~ object. It could be further extended with attack and release parameters in a similar way to levelmeter~ so that we could have ballistics.

[Nilson]

peakamp~ returns a single float number message rather than signal. I think at the moment, it is not possible to return a float number from a DSP object, we can only return signals. We could implement the peakamp functionality within Jamoma Graph - see the code for j.unsig≈ as an example