Add subcommand to print config

This subcommand has been introduced to make it easy for users to find
the location of the deprecated sled database in case they wish to delete
it. This feature should also resolve difficulties users were facing when
 trying to find where xmr-btc-swap was storing their data.

swap/src/cli/command.rs

@@ -113,6 +113,14 @@ where
             data_dir: data::data_dir_from(data, is_testnet)?,
             cmd: Command::History,
         },
+        RawCommand::Config => Arguments {
+            env_config: env_config_from(is_testnet),
+            debug,
+            json,
+            sled,
+            data_dir: data::data_dir_from(data, is_testnet)?,
+            cmd: Command::Config,
+        },
         RawCommand::Balance { bitcoin } => {
             let (bitcoin_electrum_rpc_url, bitcoin_target_block) =
                 bitcoin.apply_defaults(is_testnet)?;
@@ -248,6 +256,7 @@ pub enum Command {
         tor_socks5_port: u16,
     },
     History,
+    Config,
     WithdrawBtc {
         bitcoin_electrum_rpc_url: Url,
         bitcoin_target_block: usize,
@@ -355,6 +364,8 @@ enum RawCommand {
     },
     /// Show a list of past, ongoing and completed swaps
     History,
+    #[structopt(about = "Prints the current config")]
+    Config,
     #[structopt(about = "Allows withdrawing BTC from the internal Bitcoin wallet.")]
     WithdrawBtc {
         #[structopt(flatten)]