added helper methods for debug printing

fixed issue when reading wifi entries within old walk files
worked on earth-registration
added corresponding test-cases
other minor changes

sensors/gps/GPSData.h

@@ -38,6 +38,10 @@ struct GPSData {
 				EQ_OR_NAN(speed, o.speed);
 	}
 
+	std::string asString() const {
+		return "(lat: " + std::to_string(lat) + ", lon: " + std::to_string(lon) + ", alt: " + std::to_string(alt) + " acur: " + std::to_string(accuracy) + ")";
+	}
+
 private:
 
 	static inline bool EQ_OR_NAN(const float a, const float b) {return (a==b) || ( (a!=a) && (b!=b) );}