Low level GeoJson implementation

还没有人认领这个 Issue。

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

首先检查 services-geojson 中的当前实现，然后将其模型结构与 RFC 7946 以及链接的 Android 性能提示进行比较。定义重写版本或替代方案将如何针对大约 1,000 个 features 测量内存占用和性能；当 GeoJSON 模型在没有不必要的分配或抽象的情况下达到所要求的可扩展性目标时，即视为完成。

由索引模型根据 Issue 内容生成。