Update for protobuf version range, breaks with v3 protobuf

[3dprintscanner]

Building source as per from with the USE_MODULES=ON flag pulls in protobuf 3.3.0 and the compilation fails with message /src/caffe.pb.cc:31115:35: error: ‘MergeFromFail’ is not a member of ‘google::protobuf::internal’ ::google::protobuf::internal::MergeFromFail(__FILE__, __LINE__);

This is caused by the caffe.proto file being built against the proto 2.xx schema end emitting a c++ file with a call to MergeFromFail which was deprecated in the 3.x.x version of protobuf.

This is a temp message to show the compatibility requirements to get a functional build.

Full solution is to migrate to v3 protobuf or remove dependency entirely

edit: can remove caffe

[nudles]

if it is the problem of the proto 2.xx scheme, should fix this issue by upgrading the scheme to v3? instead of just changing the documentation?

[3dprintscanner]

if it is the problem of the proto 2.xx scheme, should fix this issue by upgrading the scheme to v3? instead of just changing the documentation?

@nudles Looks like it's possible to do that, however default values are deprecated in protobuf 3.0 and the caffe.proto file has some non-standard defaults set, not sure how those get handled in all the code consuming those objects.