Prevent codegen errors when protoc-gen-gorums version differs from imported gorums version

[johningve]

If the version of protoc-gen-gorums differs from the gorums version imported by a module, we may encounter problems with code generation. See: relab/hotstuff#28

Can we detect this in the code generator and output warnings/errors?

[meling]

We currently need to update the protoc-gen-gorums version manually. However, I've seen some interesting approaches to set the version based on tags. Will look into that.