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/src/main.rs

@@ -0,0 +1,66 @@
+extern crate slog;
+
+mod config;
+mod rpc;
+
+use std::path::PathBuf;
+
+use crate::config::LighthouseConfig;
+use crate::rpc::start_server;
+use clap::{App, Arg};
+use slog::{error, info, o, Drain};
+
+fn main() {
+    let decorator = slog_term::TermDecorator::new().build();
+    let drain = slog_term::CompactFormat::new(decorator).build().fuse();
+    let drain = slog_async::Async::new(drain).build().fuse();
+    let log = slog::Logger::root(drain, o!());
+
+    let matches = App::new("Lighthouse")
+        .version("0.0.1")
+        .author("Sigma Prime <paul@sigmaprime.io>")
+        .about("Eth 2.0 Client")
+        .arg(
+            Arg::with_name("datadir")
+                .long("datadir")
+                .value_name("DIR")
+                .help("Data directory for keys and databases.")
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("port")
+                .long("port")
+                .value_name("PORT")
+                .help("Network listen port for p2p connections.")
+                .takes_value(true),
+        )
+        .get_matches();
+
+    let mut config = LighthouseConfig::default();
+
+    // Custom datadir
+    if let Some(dir) = matches.value_of("datadir") {
+        config.data_dir = PathBuf::from(dir.to_string());
+    }
+
+    // Custom p2p listen port
+    if let Some(port_str) = matches.value_of("port") {
+        if let Ok(port) = port_str.parse::<u16>() {
+            config.p2p_listen_port = port;
+        } else {
+            error!(log, "Invalid port"; "port" => port_str);
+            return;
+        }
+    }
+
+    // Log configuration
+    info!(log, "";
+          "data_dir" => &config.data_dir.to_str(),
+          "port" => &config.p2p_listen_port);
+
+    let _server = start_server(log.clone());
+
+    loop {}
+
+    // info!(log, "Exiting.");
+}