Modified TallyEvent public interface

* Added collision and track data structs
* Added const access functions to read physics data
* Removed friend classes
Adding KDENeighborhood class for defining neighborhood region functionality
Moving points_in_box function to KDENeighborhood from KDEMeshTally
Moving point_within_max_radius function to KDENeighborhood
Moving particle weight/energy data to TallyEvent constructor
Moving KDECollision functionality to KDEMeshTally
Moving KDETrack functionality into KDEMeshTally