Call testboard directly in setRocDACs instead of another function. This
gets rid of another couple of RPC calls (roc_I2cAddr oder and over again)
some more comments
Overload api::setDAC instead of having a weird ROC parameter. Now either
use the function without the "rocid" parameter for all ROCs or take the
one with the "uint8_t rocid" parameter for a specific ROC.