Wallet operation to burn some coins (#172)

* Burn transaction for testing
* Burn bug fixes, embed burn key in keychain
* Better error logging in API, wallet fee calc fix

src/bin/grin.rs

@@ -200,6 +200,14 @@ fn main() {
 				.long("dest")
 				.takes_value(true)))
 
+		.subcommand(SubCommand::with_name("burn")
+			.about("** TESTING ONLY ** Burns the provided amount to a known \
+				key. Similar to send but burns an output to allow single-party \
+				transactions.")
+			.arg(Arg::with_name("amount")
+				.help("Amount to burn in the smallest denomination")
+				.index(1)))
+
 		.subcommand(SubCommand::with_name("info")
 			.about("basic wallet info (outputs)")))
 
@@ -313,7 +321,7 @@ fn wallet_command(wallet_args: &ArgMatches) {
 
 	// TODO do something closer to BIP39, eazy solution right now
 	let seed = blake2::blake2b::blake2b(32, &[], hd_seed.as_bytes());
-	let keychain = Keychain::from_seed(seed.as_bytes()).expect(
+	let mut keychain = Keychain::from_seed(seed.as_bytes()).expect(
 		"Failed to initialize keychain from the provided seed.",
 	);
 
@@ -371,6 +379,15 @@ fn wallet_command(wallet_args: &ArgMatches) {
 			}
 			wallet::issue_send_tx(&wallet_config, &keychain, amount, dest.to_string()).unwrap();
 		}
+		("burn", Some(send_args)) => {
+			let amount = send_args
+				.value_of("amount")
+				.expect("Amount to burn required")
+				.parse()
+				.expect("Could not parse amount as a whole number.");
+			keychain.enable_burn_key = true;
+			wallet::issue_burn_tx(&wallet_config, &keychain, amount).unwrap();
+		}
 		("info", Some(_)) => {
 			wallet::show_info(&wallet_config, &keychain);
 		}