CLIMATE-392 - Add lat/lon normalization helper

- Add Alex Goodman's helper for normalizing lat/lon grids and ensuring
  that they're monotonically increasing. This is significantly more
  robust than the current shift that is being done on dataset load.
CLIMATE-392 - Minor testing for new helper

- Add a really simple sanity check test for the new
  normalize_lat_lon_values helper. We definitely need to add more tests
  for this when time permits.
CLIMATE-392 - Use new utils helper for lat/lon clean up

- Use the utils.normalize_lat_lon_values helper for cleaning up any
  lat/lon problems when creating a new Dataset object.