Improved UART Timeout

Major:
- Improved UART Timeout: Apparently, the UART data Rx/Tx is quite unreliable (especially under motor load) leading to very often out-of-sync issues. This change allows to reset the DMA more often, leading to a faster re-sync of the UART transmission and thus avoiding UART timeout. Issue #1

Minor:
- added #define MPU_SENSOR_ENABLE to allow to enable/disable the MPU6050 sensor and save code size if the sensors is not needed
- fixed the orientation in the Processing sketch
- updated ReadMe

docs/sketch_processing/sketch_processing.pde

@@ -40,8 +40,8 @@ void draw() {
   text("Roll: " + roll + "     Pitch: " + pitch + "     Yaw: " + yaw, -200, 300);
   
   // Rotate the object
-  rotateX(radians(roll));
-  rotateZ(radians(-pitch));
+  rotateZ(radians(roll));
+  rotateX(radians(pitch));
   rotateY(radians(yaw));
   
   // 3D 0bject