Le-utils

Added
---------
* Support for `AUDIO_DEPENDENCY` format preset

Changed
------------
* Make all dependency format presets not be supplementary
* Remove all user facing strings

Added
---------
* Support for `AUDIO_DEPENDENCY` format preset

Changed
------------
* Make all dependency format presets not be supplementary
* Remove all user facing strings

------------------
- Duplicated python constants/ definitions as json files under resources/ (for easier integration with frontend)
- Added tests to make sure python constants are in sync with json constants
- Implemented first_native_name helper (used to set channel names in chefs)
- Added list-like `convertible_formats` attribute for all presets
- Added `html5_dependency` and `video_dependency` presets
- Updated constant mapping with epub -- The EPUB preset is used with document content type
- Added the following language codes:
- und = Undefined
- mul = Multiple languages
- arq = Algerian; Darja
- lkt = Lakhota; Lakotiyapi; Teton
- hdy = Hadiyya; Hadiya; Adea; Adiya; Hadia
- sid = Sidamo; Sidaamu afii; Sidaama; Sidama
- wal = Wolaytta; Borodda; Uba; Ometo

- Added file format constants for ePub
- Added RTL language lookup table in le_utils.constants.languages.RTL_LANG_CODES
- Added the following language codes:
- be-tarask = Belarusian
- hrx = Hunsrik
- lua = Luba-Kasai
- pms = Piedmontese
- sco = Scots
- rue = Rusyn

Making a new release to have a recent version. See https://github.com/learningequality/le-utils/blob/master/CHANGELOG.md for more info on changes since last release.