Define SHELL_IS_EXIST will block compliation more correctly
Unify coding style
Clean some dead code
Some code it will never enter.
Change LED's blinkly rule

I re-define new LED blink rule
LED_R: red led ON means peripherals are ready
LED_G: green led ON means correction sensor is ready
LED_B: bleu led ON means radio control signal is ready

If all of these are ready, the led will off after 1 sec
Merge branch 'free_rtos' of github.com:fboris/QuadrotorFlightControl into free_rtos