[Remote signer] Fold signer into Lighthouse repository (#1852)

The remote signer relies on the `types` and `crypto/bls` crates from Lighthouse. Moreover, a number of tests of the remote signer consumption of LH leverages this very signer, making any important update a potential dependency nightmare.

Co-authored-by: Paul Hauner <paul@paulhauner.com>

remote_signer/src/cli.rs

@@ -0,0 +1,37 @@
+use clap::{App, Arg};
+
+pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
+    // Parse the CLI parameters.
+    App::new("remote_signer")
+        .visible_alias("rs")
+        .author("Sigma Prime <contact@sigmaprime.io>")
+        .setting(clap::AppSettings::ColoredHelp)
+        .about(
+            "Simple HTTP BLS signer service. \
+            This service is designed to be consumed by Ethereum 2.0 clients, \
+            looking for a more secure avenue to store their BLS12-381 secret keys, \
+            while running their validators in more permisive and/or scalable environments.",
+        )
+        .arg(
+            Arg::with_name("storage-raw-dir")
+                .long("storage-raw-dir")
+                .value_name("DIR")
+                .help("Data directory for secret keys in raw files."),
+        )
+        .arg(
+            Arg::with_name("listen-address")
+                .long("listen-address")
+                .value_name("ADDRESS")
+                .help("The address to listen for TCP connections.")
+                .default_value("0.0.0.0")
+                .takes_value(true),
+        )
+        .arg(
+            Arg::with_name("port")
+                .long("port")
+                .value_name("PORT")
+                .help("The TCP port to listen on.")
+                .default_value("9000")
+                .takes_value(true),
+        )
+}