added offline editing demo

Examples/OfflineEditing/index.html

Examples/OfflineEditing/index.js

src/Database.js

src/Database.spec.js

src/Databases/IndexedDB.js

src/Struct.js

src/Transaction.js

src/Types/Array.js

src/Types/Array.spec.js

src/Types/Map.spec.js

src/y.js