Add possibility to force an IP configuration to an unreachable device

[danrauch]

To to so these steps seem to be necessary:

1 - Send a DISCOVERY_CMD with the flag "Allows broadcast of acknowledge" enabled (necessary flag value 0x11). 2 - Use the FORCEIP_CMD to set a temporary IP config to be able to connect to the sensor. 3 - Connect and use the bootstrap registers to set a permanent static IP config.

1 and 2 are shown in force_ip_cap.zip (Edit: Just found this python script, which implents mainly point 2: https://github.com/areaDetector/aravisGigE/blob/master/etc/pulnix/forceip.py)

3 is described in this forum (can of course be also done without adding extra functionality to aravis): https://www.freelists.org/post/aravis/initialize-point-grey-blackfly-camera,7

Thanks for your awesome work.