Add validator_node, restructure binaries, gRPC.

This is a massive commit which restructures the workspace, adds a very
basic, untested, validator client and some very basic, non-functioning
gRPC endpoints to the beacon-node.

beacon_node/db/src/lib.rs

@@ -0,0 +1,14 @@
+extern crate blake2_rfc as blake2;
+extern crate bls;
+extern crate rocksdb;
+
+mod disk_db;
+mod memory_db;
+pub mod stores;
+mod traits;
+
+use self::stores::COLUMNS;
+
+pub use self::disk_db::DiskDB;
+pub use self::memory_db::MemoryDB;
+pub use self::traits::{ClientDB, DBError, DBValue};