Added new class vtkStaticPointLocator

A new class for constructing a point locator. The class is threaded and templated for performance. It is a static locator, meaning that it can only be built once (and incremental insertion is not allowed). The code also specially treats 32-bit versus 64-bit id types for performance and to reduce memory consumption.

Additional documentation and code enhancements were made to related classes. A minor bug in vtkPointLocator related to not using the right distance measure (dist2 vs maxDist2) was also corrected.