ALM-628 adapt to small response differences with typhoeus
increased timeout value for delayed_job to 90 min
ALM-633 fixed small Postgres issues
ALM-618 further fixes for renamed article identifiers
ALM-635 updated documentation, embedded screenshots
ALM-591 updated v4 API endpoints
ALM-633 rewrote MySQL-specific functions
ALM-615 allow configuration of max. number of workers by source
add configuration example for DigitalOcean vagrant plugin
standardize how we show specific retrieval_status information with articles