feat(ElementInjector): implement ElementInjector

Initial implementation of ElementInjector.

Works:
1. The creation of proto element injector trees
2. Bindings
3. The instantiation of element injectors
4. The instantiation of directives
5. Visibility: Parent and Ancestor
6. Delegation to application injectors
7. Error handling

Missing features:
1. Handling components.
2. Setting "special" properties (e.g., Element, View).
3. Cycle detection
4. Distance
5. Text nodes
The moment you hit first key which is null, you can exist, since you know all subsequent keys will be null as well.