[WIP] Grpc and block addition

[arcolife]

Replaces socket implementation with gRPC, for:

• phase communication
• inter-node communication

Also:

• protobuf enrichment for aforementioned gRPC support
• fixes encoding issues
• Interruptable threading mechanism for each node instance
• leveldb based bank account generation/info updation
• appropriate signal handlers
• bugfixes and docstrings/inline documentation