Initial implementation in Java build by Gradle

[ocervinka]

Includes following components and functionality:

• General Telnet client (connects, disconnects, reads lines of text)
• PLCComS client based on the Telnet client
• Mqtt wrapper around Eclipse Paho MQTT client class
• YAML config file with connectivity parameters for the clients and definitions of variable to topic mappings
• When connected, queries PLCComS for current variables and subscribes to receive further variable changes
• Forwards PLC variable changes to state topics
• Consumes from command topics and sets PLC variables
• Optionally converts values using simple functions