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/config/mod.rs

@@ -0,0 +1,30 @@
+use std::fs;
+use std::path::PathBuf;
+
+/// Stores the core configuration for this Lighthouse instance.
+/// This struct is general, other components may implement more
+/// specialized config structs.
+#[derive(Clone)]
+pub struct LighthouseConfig {
+    pub data_dir: PathBuf,
+    pub p2p_listen_port: u16,
+}
+
+const DEFAULT_LIGHTHOUSE_DIR: &str = ".lighthouse";
+
+impl LighthouseConfig {
+    /// Build a new lighthouse configuration from defaults.
+    pub fn default() -> Self {
+        let data_dir = {
+            let home = dirs::home_dir().expect("Unable to determine home dir.");
+            home.join(DEFAULT_LIGHTHOUSE_DIR)
+        };
+        fs::create_dir_all(&data_dir)
+            .unwrap_or_else(|_| panic!("Unable to create {:?}", &data_dir));
+        let p2p_listen_port = 0;
+        Self {
+            data_dir,
+            p2p_listen_port,
+        }
+    }
+}