Implement more `num-traits` (e.g. checked arithmetic)

[Patiga]

The num-traits crate has many math traits which are not yet implemented in this crate for points and vectors, such as

• CheckedAdd: Add with overflow check (also all other checked operations)
• Zero and One: Additive and multiplicative identity

I am personally missing the checked operations the most, for situations where I really don't want overflows to happen and want to propagate the error with ?.

Are those methods that would be in the scope of this crate?

[nical]

Sounds good to me.

[ArtHome12]

@Patiga Can you provide examples of using Zero and One to write a test?