Changes

The general architectural idea is to start the Flow with a TraceSource, allow the connection off multiple preprocessing modules (that are both a TraceObserver and a TraceSource) and end the chain in an TraceObserver (that can be a widget or an AnalysisSource). The sigTracesChanged signal (in the TraceSource objects) is used to propagate this notification through the chain and activate a callback method (processTraces) in the ActiveTraceObserver objects (like the WaveFormWidget) to read the new data. The PassiveTraceObservers (like the AnalysisSource and the TraceRecorder widget) will ignore this signal and , so the processSignal() should be called manually.