Jesse Bounds

In https://github.com/mapbox/mapbox-gl-native/issues/7810 we saw that a developer ran into troubles when trying to resume packs via per pack KVO. In https://github.com/mapbox/mapbox-gl-native/issues/7810#issuecomment-288192116 I suggested a less complex (not per pack) approach....

Another request for an annotation animation example in https://github.com/mapbox/mapbox-gl-native/issues/8378

@jmkiley and I spent a little time investigating this so I thought I'd add some of that context while it is still in my head! There is currently an issue...

@rmnblm @1ec5 just noting that I've opened https://github.com/mapbox/mapbox-gl-native/pull/6777 to address #6159. #6777 allows you to mutate the `features` property of `MGLGeoJSONSource` and that mutation will trigger map updates. However, #6777...