Release 0.3.0

• overhaul configuration while still supporting the old one
• support of environment variables for configuration
• added better default configuration
• adjust time points in history functions to match Datomic's API
• add load-entities capabilities
• add cas support for nil
• add support for non-date tx attributes
• add Java API
• add Java interop in queries
• add basic pagination
• add noHistory support
• multiple bugfixes including downstream dependencies