Mixers& settings

Now the main part of mixers/settings/tuning logic is coded, but not tested. All settings currently are changed in the PC, and then downloaded in the radio. This is the second version of the sofware. It should still fit in the Atmega168, provided not too many settings are configured. I tried to put as few as possible limitations in the software, to allow any number of mixing and tunings. The first tests should give a better idea of the performances and if more tuning is needed. This is going to be interesting !