bindingType property Null safety

1. conduit_core
2. conduit
3. Bind
4. bindingType property

Bind class

1. Constructors
2. body
3. header
4. path
5. query
6. Properties
7. accept
8. bindingType
9. hashCode
10. ignore
11. name
12. reject
13. require
14. runtimeType
15. Methods
16. noSuchMethod
17. toString
18. Operators
19. operator ==