CLI API refactoring and improvement (#4692)

It changes the way we extended the CLI functionalities of substrate to allow more flexibility. (If this was not clear, here is another version: it changes the `sc_cli` API to allow more flexibility).

This touches a few important things:
 - the startup of the async task with tokei:
    This was in node and node-template and I moved it to substrate. The idea is to have 1 time the code that handles unix signals (SIGTERM and SIGINT) properly. It is however possible to make this more generic to wait for a future instead and provide only a helper for the basic handling of SIGTERM and SIGINT.
 - increased the version of structopt and tokei
 - no more use of structopt internal's API
 - less use of generics

Related to #4643 and https://github.com/paritytech/cumulus/pull/42: the implementation of "into_configuration" and "get_config" are similar but with better flexibility so it is now possible in cumulus to have the command-line arguments only of the run command for polkadot if we want

Related to https://github.com/paritytech/cumulus/issues/24 and https://github.com/paritytech/cumulus/issues/34 : it will now be possible to make a configuration struct for polkadot with some overrides of the default parameters much more easily.

substrate/bin/node/cli/src/command.rs

@@ -0,0 +1,82 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use sc_cli::{VersionInfo, error};
+use sc_service::{Roles as ServiceRoles};
+use node_transaction_factory::RuntimeAdapter;
+use crate::{Cli, service, ChainSpec, load_spec, Subcommand, factory_impl::FactoryState};
+
+/// Parse command line arguments into service configuration.
+pub fn run<I, T>(args: I, version: sc_cli::VersionInfo) -> error::Result<()>
+where
+	I: Iterator<Item = T>,
+	T: Into<std::ffi::OsString> + Clone,
+{
+	let args: Vec<_> = args.collect();
+	let opt = sc_cli::from_iter::<Cli, _>(args.clone(), &version);
+
+	let mut config = sc_service::Configuration::default();
+	config.impl_name = "substrate-node";
+
+	match opt.subcommand {
+		None => sc_cli::run(
+			config,
+			opt.run,
+			service::new_light,
+			service::new_full,
+			load_spec,
+			&version,
+		),
+		Some(Subcommand::Factory(cli_args)) => {
+			sc_cli::init(&mut config, load_spec, &cli_args.shared_params, &version)?;
+
+			sc_cli::fill_import_params(
+				&mut config,
+				&cli_args.import_params,
+				ServiceRoles::FULL,
+				cli_args.shared_params.dev,
+			)?;
+
+			match ChainSpec::from(config.expect_chain_spec().id()) {
+				Some(ref c) if c == &ChainSpec::Development || c == &ChainSpec::LocalTestnet => {},
+				_ => panic!("Factory is only supported for development and local testnet."),
+			}
+
+			let factory_state = FactoryState::new(
+				cli_args.mode.clone(),
+				cli_args.num,
+				cli_args.rounds,
+			);
+
+			let service_builder = new_full_start!(config).0;
+			node_transaction_factory::factory::<FactoryState<_>, _, _, _, _, _>(
+				factory_state,
+				service_builder.client(),
+				service_builder.select_chain()
+					.expect("The select_chain is always initialized by new_full_start!; QED")
+			).map_err(|e| format!("Error in transaction factory: {}", e))?;
+
+			Ok(())
+		},
+		Some(Subcommand::Base(subcommand)) => sc_cli::run_subcommand(
+			config,
+			subcommand,
+			load_spec,
+			|config: service::NodeConfiguration| Ok(new_full_start!(config).0),
+			&version,
+		),
+	}
+}