GitLab

Update to finalized protobuf format.
Also remove deprecated selector interface which is out of date

Add ToNet and FromNet functions that read/write to an io stream for use in network. Also type
response codes

Use a Cid as a root instead of a node, so that only one round trip is neccesary

Initial implementation of graph sync messages including protobuf struct and
serialization/deserialization

fix #2 fix #3