Implemented a PID loop to hold the motor level.

I experimented with values for the PID coefficients. I was satisfied after seeing a proper rise time and seeing the drone motor flying stably level. I believe I could improve smoothness by averaging the accelerometer values. Also, I could make 2 separate states with different coefficients, one to quickly accelerate the motor PWM before the motor turns (from 0%-~40% duty cycle), then to continue rising slowly and in a controlled way to maintain a stable and level condition. Already knowing this, I will contemplate future goals for this project.