Added Area FromCircle methods

[gojanpaolo]

Fixes #377

Concerns:
How to handle negative radius/diameter

1. Should we throw exception?
2. Should we just ignore (or absolute value)?
   • Current implementation is ignored which implicitly gets absolute value since it squares the value

Need to add tests either case.

Note:
High precision area of circle online calculator

[angularsen]

Hm, since the default behavior is that of absolute value, I see no reason to handle this specifically so I think we should simply allow it.

[angularsen]

Ok maybe I merged a bit early if you intended to add test case for the negative values, can add that separately I guess :-) Sorry!

[gojanpaolo]

Ahh lol. That's fine. We can add the test case next time. Implementation will not change anyway. :)
Thank you!