V2.5.6 stable (#10961)

-  Fix cargo audit (#10921)
  - Add support for Energy Web Foundation's new chains (#10957)
  - Kaspersky AV whitelisting (#10919)
  - Avast whitelist script (#10900)
  - Docker images renaming (#10863)
  - Remove excessive warning (#10831)
  - Allow --nat extip:your.host.here.org (#10830)
  - When updating the client or when called from RPC, sleep should mean sleep (#10814)
  - added new ropsten-bootnode and removed old one (#10794)
  - ethkey no longer uses byteorder (#10786)
  - Do not drop the peer with None difficulty (#10772)
  - docs: Update Readme with TOC, Contributor Guideline. Update Cargo package descriptions (#10652)

parity/cli/mod.rs

@@ -300,7 +300,7 @@ usage! {
 
 			ARG arg_chain: (String) = "foundation", or |c: &Config| c.parity.as_ref()?.chain.clone(),
 			"--chain=[CHAIN]",
-			"Specify the blockchain type. CHAIN may be either a JSON chain specification file or ethereum, classic, poacore, tobalaba, expanse, musicoin, ellaism, mix, callisto, morden, ropsten, kovan, rinkeby, goerli, kotti, poasokol, testnet, or dev.",
+			"Specify the blockchain type. CHAIN may be either a JSON chain specification file or ethereum, classic, poacore, volta, ewc, expanse, musicoin, ellaism, mix, callisto, morden, ropsten, kovan, rinkeby, goerli, kotti, poasokol, testnet, or dev.",
 
 			ARG arg_keys_path: (String) = "$BASE/keys", or |c: &Config| c.parity.as_ref()?.keys_path.clone(),
 			"--keys-path=[PATH]",