Implemented PID on Rotationnal Rate
-Implemented Stabilized PID
it is a cascade PID controller angle->rate
Finetuned PID parameters are now set during the initialization
The choice off stabilized of Rate PID can be done by commenting
specific #define in the timer.cpp

-Added a servoStop() function in servo class

-Bug fixes:
MPU6050 rate scale was set incorrectly leading to overshoot in angle
Pitch and Roll offset are now back du to improper raw values
Stabilized PID