fixed some issues with stats::variance

fixed umbrella header for stats
added error-feedback to wifi optimizers
improved logging for wifi optimizers
adjusted calling-API for wifi-optimizers

math/Stats.h

@@ -5,5 +5,6 @@
 #include "stats/Median.h"
 #include "stats/Minimum.h"
 #include "stats/Maximum.h"
+#include "stats/Variance.h"
 
 #endif // MATH_STATS_H

math/stats/Variance.h

@@ -37,7 +37,7 @@ namespace Stats {
 
 		/** get the current stadard-deviation */
 		Scalar getStdDev() const {
-			return std::sqrt(get);
+			return std::sqrt(get());
 		}