Add polygon support for ios and android.

At Sitata, we've been experimenting with adding polygon support. Please check this out and let us know what you think. It could use a second look at things.

  - Polygons can be specified on mapview creation.
  - addPolygon, removePolygon, and removeAllPolygons methods.
  - points can be specified as an object (verbose!) or as an array.
  - version bump for both platforms.