* Skip empty files for local, hdfs, and cloud input sources
* split hint spec doc
* doc for skipping empty files
* fix typo; adjust tests
* unnecessary fluent iterable
* address comments
* fix test
* use the right lists
* fix test
* fix test
* Move Azure extension into Core
Moving the azure extension into Core.
* * Fix build failure
* * Add The MIT License (MIT) to list of compatible licenses
* * Address review comments
* * change reference to contrib azure to core azure
* * Fix spelling mistakes.