Improve all API documentation

[chapulina]

Desired behavior

• Check spelling
• Mention units where needed
• Add examples to the API doc
• Make sure descriptions are meaningful, and not just

/// \brief Sets A.
void SetA(int _a)

Alternatives considered

N/A

Implementation suggestion

1. Angle
2. AxisAlignedBox
3. Box
4. Color
5. Cylinder
6. DiffDriveOdometry
7. Filter
8. Frustum
9. GaussMarkovProcess
10. graph/Edge
11. graph/GraphAlgorithms
12. graph/Graph
13. graph/Vertex
14. Helpers
15. Inertial
16. Kmeans
17. Line2
18. Line3
19. MassMatrix3
20. Material
21. MaterialType
22. Matrix3
23. Matrix4
24. MovingWindowFilter
25. OrientedBox
26. PID
27. Plane
28. Pose3
29. Quaternion. See pull request #327.
30. Rand
31. RollingMean
32. RotationSpline
33. SemanticVersion
34. SignalStats
35. Sphere
36. SphericalCoordiantes
37. Spline
38. Stopwatch
39. Temperature
40. Triangle3
41. Triangle
42. Vector2
43. Vector3
44. Vector3Stats
45. Vector4

Additional context

This was broken off #101.