AT Labs RM-2 MeshCore 1.16.0.AT.1

Based on MeshCore 1.16.0 with RM-2 hardware support and an 8 dBm
transmit-power limit.

Available builds:

- Companion BLE
- Companion USB
- Companion Dual
- Repeater with GPS off
- Repeater with GPS on

Companion Dual supports BLE and USB in one image. USB takes priority while a
USB session is open.

GPS can run continuously with `gps interval 0`, or wake on a schedule with
`gps interval <seconds>`.