docs(NgAnnotation): copyedit and example fix

Closes #849
refactor(NgValue): use the @NgDirective module feature

- Use the @NgDirective module feature to inject an NgValue
instance into OptionValueDirective and InputRadioDirective when
no `ng-value` attribute is present. This results in a much
cleaner design.
- Update `ng-value` API documentation.

Closes #848
fix: imports

Closes #847
refactor(Tests): Refactor tests not to use $.

Closes #844