Fixed issue with removing points from index and rebuilding the index. Some performance improvements when no points have been removed

Several refactorings related to incremental index constructions.
Reverting to regular polymorphism as the CRTP speedups are not worth the
comprexity and increase in compilation times.

Memory leaks in hierarchical_clustering_index.h

Fixed memory leaks.

Add /bigobj WIN32 compile flag 

fix bug in lsh_table under C++11 and gcc