Implement Qr-code to export Mosquito strategy and settings

In the future, we could embed more text (strategy parameters, etc.), thanks to a QRcode with a lib like this one https://pypi.python.org/pypi/qrcode
I think the limit a QRcode can handle is around 4296 characters. So with a compact representation of all parameters, we could certainly embed all parameters necessary to share to someone the exact mosquito settings just by sending him the PNG ;-)