issue #1 - update code in order to use the java7 utilities
issue #2 - replace derby with mapdb
issue #2 - refactor unused classes; improve configuration
issue #2 - fix test; some optimizations
issue #2 - fix test
issue #2 - change data structure
issue #2 - mark new property "key" as ignorable by JSON serializer
issue #2 - save database state while application is shutting down
issue #2 - add context-based transaction manager
issue #2 - create context if not exists
issue #2 - implement transaction management
issue #2 - fix mocked fields loading
issue #2 - optimize imports
issue #2 - async update data
issue #2 - restore explicit database shutdown
issue #2 - serialize MockedField explicitly as MockedFieldImpl
issue #2 - remove MockedField.id