Add a LOS feature that tracks the quad

[CurryKitten]

Several requests for a LOS feature. This shouldn't be too difficult to implement along with a feature that attempts to hold the quad in view at all times.... as if you the pilot would be turning to making sure you could always see the quad.

[CurryKitten]

Whilst this feature is technically done, flying LOS exposed a few things that didn't look right that did in FPV. The gravity seems too much, and the power seems way too much - it's very hard to hold a hover. Bringing the gravity down to 0.6 and the throttle to 0.25 felt better, but the quad was still a handful

It also led me to rethink the idea of self-leveling modes. I don't really fly LOS in acro, so I'm going to add and angle/horizon feature to make things easier.

[CurryKitten]

Got this to a stage where I'm happier with the LOS mode, and something resembling angle mode as well which makes things easier. There was an issue when playing on a screen that it's very easy to lose the quad. It gets small much quicker than in real life, so I made a zoomed in window as a second camera that gives a zoomed in view which helps show the orientation of the quad.