Store perimeter polygons with approrpriate nesting

[jdubowy]

We currently accept and store perimeter polygons as an array of coordinates:

  "polygon": [
    [-122.45, 46.43],
     [-122.39, 46.43],
    ...

We should store them as an array of array of coordinates

  "polygon": [
    [
      [-122.45, 46.43],
      [-122.39, 46.43],
       ...

This is consistent with the geojson standard for polygons and it supports holes.

• [x] update Location object instantiation to convert reduced nesting depth to increased depth (for backward compatibility
• [x] update all code that uses fhe polygon coordinate data to expect the increased nesting depth
  • [ ] fuelbeds
  • [x] locationutils.LatLng
• [x] update unit tests
• [x] update regression tests