Expose and unit test DataLoaderUtil#resolveFileExtension.
Refactor JSON-support out of CSVDataLoader and into a CSV-JSON-specific Loader.

1. Move value normalization that is specific to JSON into CSVJSONDataLoader
2. Connect all the creation Loader creation bits
  i. add tests for LoaderFactory
  ii. add tests for file extension -> LoaderType resolution
3. Add a test that verifies characters are supported for CSV per rules of rfc4180
Merge branch 'issue-1-refactor-approach-to-CSVLoader-json-support'

Resolves issue #1