Generate client API based on protobuf definitions

[bobvanderlinden]

As discussed in #44, to keep up with changes on machinetalk-protobuf it would be helpful to generate API code from protobuf definitions. This can be done once a base has been defined as described in #44.

Once the base is defined, we have a way to update several kinds of status objects (MT_FULL_UPDATE) and a way to call commands and request data (MT_REQ, MT_ACK, MT_NACK). These status objects and commands need to be defined in a way so that a generator can create code for Python, Javascript and C/C++.

[machinekoder]

@bobvanderlinden This might be a little miss misunderstanding. I want to generate the code not from the protobuf spec but from a model for the protocol. However, this model should also be used to document the messages, as this is very essential for a protocol. My tests so far are very promising.

A single model can be used to create binding for various languages (just add a code generator) and documentation with a single model. If it works out that would drastically simplify creating new protocols with Machinetalk and maintaining them.

[machinekoder]

Here is my attempt: https://github.com/strahlex/machinetalk-gsl