Add Polyline and Polygon drawing using MapData sources

[msmollin]

Currently we utilize the Marker interface to draw polyline and polygon structures here: https://github.com/mapzen/ios/blob/master/MapzenSDK/Marker.swift#L66

While this isn't an issue, after discussion with @tallytalwar in the long term the recommendation is to use the MapData source interface here: https://github.com/tangrams/tangram-es/blob/master/platforms/ios/src/TangramMap/TGMapData.h to construct those items.

My thought is, unless the Marker interface for those objects is being deprecated, we leave the current implementation as is, and just add the MapData objects to be used for similar purposes.

Thoughts? cc @matteblair / @karimnaaji / @sarahlensing