Fix cloudsearch define-index-field for type latlon

Was making an incorrect assumption on how the ``--type`` for  ``aws cloudsearch define-index-field`` was being mapped to the service model.  Specifically,``latlon`` was being mapped to ``Latlon``, but in the serivce model, it is ``LatLon``.  The assumption in the mapping we make is that all capitalization should happen whenever there is a hyphen in the value of ``--type``.  For example, ``date-array`` is mapped to ``DateArray``.  But this does not hold for ``latlon``

Fixes https://github.com/aws/aws-cli/issues/929

cc @jamesls @danielgtaylor