Radius class

1. Constructors
2. circular
3. elliptical
4. Properties
5. hashCode
6. x
7. y
8. runtimeType
9. Methods
10. toString
11. noSuchMethod
12. Operators
13. operator %
14. operator *
15. operator +
16. operator -
17. operator /
18. operator ==
19. operator unary-
20. operator ~/
21. Static methods
22. lerp
23. Constants
24. zero