[Overview] Refactor

[htdvisser]

This issue is an overview of the refactor branch and the related features and fixes.

• Service Discovery (Broker Discovery #71)
• Lower bufferDelay in Handler (Lower bufferDelay in Handler #72) - is now 200ms.
• gRPC over TLS (Use of TLS in grpc #85)
• gRPC Error Handling (RPC Error handling #89)
• Migrate the network controller to a dedicated component (DevAddr and Network config should be determined by Broker, not Handler. #90 and Migrate the network controller functionality to a dedicated component #109)
• Gateway Protocol Abstraction (Support Semtech gateway protocol v2 #96)
• Handle uplink for frequencies that are not supported (Don't drop uplink when frequency is not supported #98)
• Migrate from Bolt to Redis (Add Redis storage adapter #100)
• Airtime calculation (Airtime, Duty-Cycle and Fair-Use calculation package #101)
• Handling extra info in Gateway status messages (Handling extra info in gateway status messages #117)
• Support for US and AU Frequency Plans (Support for US 915 #119 and Support for Australia 915-928 #120)
• Downlink port number (Add port for mqtt downlink #127)
• Don't schedule downlink on gateways that can't do downlink (Don't schedule downlink on single-channel gateways #140)
• Handle both 16 and 32 bit frame counters correctly (16 bit counters not handled correctly #153)
• Downlink "Encoder" Payload Function (Add encoder payload function #195)
• Use clean sessions for MQTT client (Disable persistent sessions in MQTT #203)
• MAC commands (Support for MAC commands #41)
• ADR
• Advanced MQTT publishes (Events on MQTT #159, Publish decoded payload fields as MQTT topics #193 and Decorate device activation event #194)
• Support for FSK modulation (Support for FSK modulation #171)

[htdvisser]

With refactor being renamed to v2-preview and all checkboxes being checked, this issue can be closed.