MDL-35073 badges: Open badges integration

The badges feature allows to integrate Mozilla "Open Badges" to issue, assign,
manage and display digital badges in Moodle. This feature supports:
-- badge creation and issuing based on criteria
-- badge baking and verification service
-- direct pushing of internal badges to external backpack
-- interanl and external badge display in Moodle
-- Moodle block to display latest badges