horus: add model locator by RSSI (to find lost/crashed plane)

[offer-shmuely]

This widget help to find a lost/crashed model based on the RSSI (if still available)
The widget produce audio representation (variometer style) of the RSSI from the lost model
The widget also display the RSSI in a visible colorized bar (0-100%)

There are two way to use it

1. The simple way:
   walk toward the quad/plane that crashed,
   as you get closer to your model the beeps will become more frequent with higher pitch (and a visual bar graph as well)
   until you get close enough to find it visually

2. the more accurate way:
   turn the antenna straight away (i.e. to point from you, straight away)
   try to find the weakest signal! (not the highest), i.e. the lowest RSSI you can find, this is the direction to the model.
   now walk to the side (not toward the model), find again the weakest signal, this is also the direction to your model
   triangulate the two lines, and it will be :-)

[offer-shmuely]

[pfeerick]

Oh, very handy! Just needs some "no, getting colder", "yup, keep going that way, getting warmer" and "yikes, getting hot, mind where you put your feet" (especially when looking for tiny whoop quadcopters in the long grass) commentary 😆