refactored database

src/Connector.js

src/Connectors/Test.js

src/Database.js

src/Database.spec.js

src/Databases/IndexedDB.js

src/Databases/IndexedDB.spec.js

src/Databases/Memory.js

src/Databases/RedBlackTree.js

src/Databases/RedBlackTree.spec.js

src/Transaction.js