refs #2509: Create categories.json file for migration
refs #2509: Add test for Categories vocabulary
refs #2509: Add Categories taxonomy to osha_taxonomies
refs #2509: Add tests for Category migration
refs #2509: Add categories migration class
refs #2509: Map categories migration
refs #2509: Add migration import for Categories in the install script
Add new data in source categories.json and change the tests in order to fit the new data
refs #2509: Remove the Categories taxonomy, and replace it with the default tags one
refs #2509: Refactored the migration machine name
refs #2509: Add more translations and updated the test accordingly
refs #2509: Removed whitespaces cf. code review
refs #2509: Removed the tags vocabulary test
Merge pull request #31 from razvan-tache/task_2509

Refs #2509: Add Category taxonomy and migration to the site