feat: iterate on SsfStepDetector

* use SSF signal instead of accelerometer signal
* use higher BEAT_CORR_THR_{12} for SSF signal
* add absolute SSF_THRESHOLD to ignore small accelero bumps
* compute ssf_threshold according to detected SSF peaks, not the mean (more robust vs. noise)

pasada-lib/include/pd_signal.h

@@ -6,6 +6,7 @@
 #define PASADASUPERPROJECT_SIGNAL_H
 
 #include <vector>
+#include <deque>
 
 namespace pd_signal {
     /** `num` evenly spaced numbers over interval [start,stop] */
@@ -33,6 +34,8 @@ namespace pd_signal {
 
     /** two-dimensional mean of a collection of signals */
     void mean(std::vector<double> &out, std::vector<std::vector<double> >& m);
+    /** two-dimensional mean of a collection of signals */
+    void mean(std::vector<double> &out, std::deque<std::vector<double> >& m);
 
 }