Point locator

We came across a situation where we needed a PointLocator that only locates points in local elements and returns NULL otherwise.  This branch implements this capability without impacting the existing default PointLocator behavior, which searches over all active elements.  The first "code formatting" patch 0bb52c4 was just some stuff I fixed while I was investigating this PointLocator update, the actual changes to PointLocator are in 96e1eaa.