Moved configuration around for validator client.

- Custom datadir/server argument logic moved into configuration, out of main.
 - Updated the validator config directory structure, as per issue #253 suggestions
 - Removed the 'generate 3 random keys' function
 - Updated the README to reflect new structure
 - Just exit if there are no keys, don't generate any (this is for accounts_manager, in a separate commit).
 - Created a lib.rs file, so that the validator client configuration can be included by external crates.

validator_client/Cargo.toml

@@ -4,6 +4,15 @@ version = "0.1.0"
 authors = ["Paul Hauner <paul@paulhauner.com>"]
 edition = "2018"
 
+[[bin]]
+name = "validator_client"
+path = "src/main.rs"
+
+[lib]
+name = "validator_client"
+path = "src/lib.rs"
+
+
 [dependencies]
 block_proposer = { path = "../eth2/block_proposer" }
 bls = { path = "../eth2/utils/bls" }