OMB should support targets implementing a single duo-LED for communication stack use

Currently the AP task of the stack handles two separate duo-LEDs.
In order to use the stack with targets that provide only a single duo-LED, the stack should support a "combined" LED behavior.

The proposal is that the stack should detect if the LED settings in the startup parameters of the AP task are the same for both duo-LEDs configured. In this case it should apply the "combined" LED behavior.