fix android build, now uses c++_shared
include android support as system headers to silent useless warnings
remove misleading include toolchain file for android
Allow tiles to be skipped in draw loop when they are null (i.e. loading)
Provide getters for the number of vertices and indices in a VboMesh
Remove cached tesselator instance and instead instantiate tesselators on demand (tesselator is not thread-safe)
Modify PolygonStyle methods for thread safety; No member values can be written within addData
Modify DataSource to retrieve only one tile at a time, with the intention of spawning this process in background threads
Use c++11 async functions to fetch and build map tiles asynchronously from TileManager;

TileManager spawns a new task for each tile request using a lambda, then polls the status of incoming tile tasks during each update loop
Delete tesselator instance after usage (was being leaked)
DataSource now uses cached tile data if present;

Currently, tile data is all effectively indefinitely cached
Cleaner iterator usage when removing elements from a collection while iterating
Merge branch 'master' into async-tiles;

Reorganized some of the new and renamed methods into the newly separated DataSource subclasses

Conflicts:
	core/src/dataSource/dataSource.cpp
	core/src/dataSource/dataSource.h
	core/src/tileManager/tileManager.cpp
update gitignore
makefile for cmake build
remove android definitions from toolchain
Discard Json tile data immediately after tile construction (i.e. zero caching)
remove android definitions from toolchain #2
update makefile
don't replace xcode project