Improved navigation within sub-arcs.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1554655 13f79535-47bb-0310-9956-ffa450edef68
Finalized 1-sphere.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1554656 13f79535-47bb-0310-9956-ffa450edef68