Add generic converter plugin and python producer example for it

Implementation of a generic converter plugin that can be used by nonspecific DUT.
It is based on data conversion at producer and binary serialization using protocol buffers.
Added python example making use of it and fixes few issues related to python producer.

It is most likely not fastest but is suitable for small prototype devices. No need to touch any eudaq code to integrate (hopefully).

To enable need to install protocol buffers and add -DGEN_proto=ON to cmake command