Low level GeoJson implementation

まだ誰も着手していません。

This is a request for either a rewrite or alternative implementation of the current GeoJson module found [here](https://github.com/mapbox/mapbox-java/blob/master/services-geojson). We need a high performance implementation that has a minimal memory footprint. The reasoning behind that is that geojson models should be scalable (eg. downstream we query the map for 1000 of features, the path currently taken to create those and the intermediate objects created for doing that isn't optimal atm).

Couple of thoughts to improve this:
- use primitive instead of objects where possible
- no need for AutoValue, implementation is based on a specification that doesn't change (often)
- if geojson models are immutable, use arrays instead of List
- limit method invocations & don't allocate memory if you can avoid it
- don't over abstract concepts if they can be expressed more simple

More information on performance tips [here](https://developer.android.com/training/articles/perf-tips.html)
RFC of GeoJSON can be found [here](https://tools.ietf.org/html/rfc7946).

cc @mapbox/android

まず services-geojson の現在の実装を確認し、次にそのモデル構造を RFC 7946 およびリンク先の Android パフォーマンスに関するヒントと比較します。約 1,000 個の features を対象に、書き換えまたは代替実装でメモリフットプリントとパフォーマンスをどのように測定するかを定義します。GeoJSON モデルが不要なアロケーションや抽象化なしに、要求されたスケーラビリティ目標を満たせば完了です。

索引モデルが issue の本文から書いたものです。