[MATH-749] Add MonotoneChain implementation.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1563284 13f79535-47bb-0310-9956-ffa450edef68
Improve tests.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1563285 13f79535-47bb-0310-9956-ffa450edef68