Merge pull request #11 from fdiller/master

register now uses a URL instead of IP+port
Remove ip and port from Hello as useless.
Merge pull request #12 from dchilot/bugfix/clean-hello

Remove ip and port from Hello as useless.
add image field in register message to pass an image of the ball/tank
for the image processing on server side
Merge pull request #13 from fdiller/feature/image-in-register

add image field in register message to pass an image of the ball/tank