Add annotation movement example

[friedbunny]

Fixes #24. This is a very rough example that’s not ready for prime time. For now, this is a proof of concept.

The performance problems with this example are tracked upstream in mapbox/mapbox-gl-native#5645.

See AnnotationMovementExample.swift for the initial implementation.

Notes

• The GeoJSON track has been smoothed by adding points at evenly spaced intervals.
• If interaction is disabled, this example is fine.
• If you pan the map, the annotation view lazily lags behind, then catches up.
• Zooming, panning, and rotating all cause the annotation to veer off course.
• Simply setting the center coordinate of the map view works fairly well.
• Animating the view and the map center is very expensive — 30-40% CPU on my iPhone 6s.

/cc @frederoni @1ec5 @pveugen

[friedbunny]

Here’s a video of this first cut in action. It’s entertaining, but bad. Dragging the map and having it snap back is oddly satisfying...

[friedbunny]

I plan on coming back to this once mapbox/mapbox-gl-native#6215 is widely available.

[1ec5]

This code needs to be eviscerated along the lines of #78, now that GeoJSON deserialization is built into the SDK.

[friedbunny]

So very stale.