ThingsBoard IoT Gateway

What's Changed

Added minor fixes for modbus connector.
Fixed error with logLevel key in connector configuration.

Added backing up for connectors configuration files on update and tb_gateway.json on remote configurator start.

• Fixed send_current_configuration method by @samson0v in #1183
• Fixed modbus slave init by @samson0v in #1192

Full Changelog: 3.4...3.4.1