Renamed FastKdTreeAllocator file and class to match coding conventions

+Add: Usage of Memory Allocator in building strategy
~Change: Private methods in building strategy changed to use
FastKdTree-Nodes
~Change:Removed inheritance from KDTreeBuildingStrategy. Didn't delete
 the file, though. Could be reintegrated later.
+Add: method declaration to fast kd tree in order to add the triangle
 iterators. Just a proposal. Give me feedback (See comments)
+Add: Size macro for Memory Allocator. One can specify the size of
 the allocators array with -DFASTKDTREEALLOCSIZE=<size> in the compiler
 flags.