Refactored DB collections.
Exposed Jackson mapper.
Added Jackson mapper per DB instance, removed JSON module dependency.
Removed dependency of in-mem DB to the U utils.
Minor improvements of the DB API.
Implemented custom JSON serialization (only the IDs) of the DB collections.
Added test for the DB collections persistence.
Simplified transaction demo due to the built-in transactions in apps.
Improved add-ons configurations and introduced "full" config option.
Improved construction of anchors with icons.