eda: setup a recovery protocol when sync is lost

[sbinet]

it may happen that the eda/rfm <=> sdhcal-daq link loses synchronization.

currently, the happy path is:

RFM -> [HDR\0 <size-u32>] -> DimEDA
RFM <- [ACK\0]            <- DimEDA
RFM -> [payload]          -> DimEDA
RFM <- [ACK\0]            <- DimEDA

we need to devise a protocol for when RFM receives a NAK\0 message: it should try to recover and re-send data (probably n-times).

ideas:

• drop the whole connection and create one anew
• rely on ZeroMQ or NanoMSG