Resolves#330
- removes `unbind` from the binder and moves it to the `Binding` instance itself;
- `Binding` is now an interface with a default implementation provided by SCS
- Removed all methods from Binder except for unbind()
- Removed old and unused code
- Removed circular reference between default Binder and Binding implementations
- Removed Binder type
6c880726b8