Camera rework

@kadst43 @eric79 

This should be finished, pending the review. This runs off of `vwf/mars-game-staging` and does not use the navigable changes I was attempting to make. It's similar to the `targetFollower/camera` model, but with the camera mount system we talked about.

I rewrote the camera pan functionality using the new system and I changed the delay from 17 seconds to 3 seconds (this can be tweaked). I know the delay is supposed to sync up with the VO, but it doesn't really and it's too long so when it pans after 17 seconds it feels like a bug. I think the user gets the point if the camera shows them the radio and then the VO tells them to travel to it.

I also rewrote the navigation modes so that we aren't messing with the `matrixWorld` directly.
Let's get in the habit of putting a brief comment at the top of each file - or at least of major files - describing roughly what the contents of the file do. This is especially handy as you build more complex systems that have a bunch of moving parts like this...