Add plugin‑level hardware‑specific configuration support

This plugin should handle its own hardware‑specific configuration by providing a
`core/config/specific.config.ini` file with the following content:
```
[atlas]
  z2m[controller] = ezsp
  z2m[port] = /dev/ttyS2
  z2m[z2m::mode] = local

[luna]
  z2m[controller] = ember
  z2m[port] = /dev/ttyLuna-Zigbee
  z2m[z2m::mode] = local
```