Data Type - Quaternion

[npruehs]

Implement an immutable Quaternion struct in the Core folder.

• Write a struct summary comment.
• Add the CLSCompliant attribute.
• Implement IEquatable
• Implement Equals and GetHashCode.
• Implement equality operator overloads.
• Implement ToString.
• Provide a static readonly field for the zero quaternion.
• Implement operator overloads.