BSP tree now provide an API to compute a global signed distance.

The distance is defined from a test point to the region. It is positive
if the point is outside of the region, negative if the point is inside,
and zero when the point is at the boundary. The distance is continuous
everywhere, so it can be used with a root solver to identify accurately
boundary crossings. This API is available for all BSP trees, in
Euclidean and spherical geometries, and in all dimensions.

Fixes MATH-1091

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1560115 13f79535-47bb-0310-9956-ffa450edef68