v2.3.18

• maintenance mode #325
• forbid to set a channel function that is not supported by its type 163a040
• fix redirection to login page when invalid token is stored in the browser 73207bb
• display account server in account details page 90a7a14
• display IO device version in IO device details page 231d115
• convert IP addresses inside database #349
• upgrade Symfony 3.4.30 to 3.4.37 #329, enable the application to work in PHP 7.3 environment