1. Renamed GetResponse to Query in DGraph service.
2. Client now accepts the ip of the server as a flag instead of just the port.
3. Removed ToProtocolBuffer method, and added PreTraverse as a method for a Subgraph.
4. Renamed runServerForClient to runGrpcServer.

Client now gets back protocol buffer data and is able to parse it into protocol buffer Subgraph

1. Added subgraph.proto file which has the message structure.
2. Added ToProtocolBuffer method which converts a subgraph to protocol buffer.

Remove gql module's dependency on query. Make it the other way round. GraphQL query string, now gets converted into query.SubGraph as an additional step run via query.ToSubGraph.

Use cache for streaming entries instead of opening files for each posting list. Use iterator instead of channel while streaming entries.

Loads of fixes and tweaks to make data loading work. Largely, the system is really fast in inserting data, but memory becomes a problem. So, running continuous memory checks, and if the db exceeds set memory, then stopping in world in batch load mode to deal with it first. In server mode, same code runs but without stopping the world.

Handle reading rdf data from files. Use underscores for uid and xid, keeping it in sync with internal usage. Output uids as hex.