some fixes [multithreading,..]

needed interface changes [new options]
logger for android
wifi-ap-optimization
new test-cases

sensors/imu/AccelerometerData.h

@@ -2,6 +2,8 @@
 #define ACCELEROMETERDATA_H
 
 #include <cmath>
+#include <sstream>
+
 
 /** data received from an accelerometer sensor */
 struct AccelerometerData {
@@ -40,6 +42,12 @@ struct AccelerometerData {
 		return AccelerometerData(x/val, y/val, z/val);
 	}
 
+        std::string asString() const {
+            std::stringstream ss;
+            ss << "(" << x << "," << y << "," << z << ")";
+            return ss.str();
+        }
+
 };
 
 #endif // ACCELEROMETERDATA_H