build process : Add clean target
Arduino - update the circuit + ready signal

- Add leds to improve visual output and change pins
- Add ReadyToLoop() who blink on start
Arduino - Add "Quit" feature

- Add quit pushbutton who send "QUIT" msg over serial
yvonne remote lib : Add strstr_last

* strstr_last : search in a string for the last occurence
of a substring
yvonne remote : add QUIT state, update ffmpeg cmd line, use of strstr_last

* QUIT state stop cleanly the loop and exit the program, from the remote over serial
* ffmpeg : use of "-vcodec mjpeg" option to generate an avi (prefered codec for veejay software)
* strstr_last is used to read multiple concatenated order that can occur over serial ex: "STOPVIDEOSTART"
will generate the video without stopping the shoot.
yvonne remote : what a nice buffer overflow!