GCS Control fix

This fixes using the GCS Controller widget on next. The main bug
was that it tried to configure all the channels including the armed
channel but was not using them properly. Now it only configures the 
control channels the widget actually sets appropriately.

Also this cleans up some of the options:
- "GCS Receiver" in the options page. Now this makes it possible or not to take control. This is a useful safety feature as one would not want to accidentally take control from GCS in flight.
- Rename the Enable check box to "Take control" to indicate what it does