Preserve /etc/config/system and /etc/config/network

[nemesifier]

When setting up both the controller and a new device type for the first time, it is annoying that /etc/config/system and /etc/config/network are overwritten by the configuration downloaded from the controller, this requires unnecessary duplication in maintaining the ntp configuration, led settings, and the basic ethernet configuration both on the device and on the controller.

A possible solution would be to store the original system and network configurations and merge them with the configuration downloaded by the controller.

This feature could be enabled by default but it could be possible to disable it if needed (like #10).

[nemesifier]

It works!