Adding HNSW-QG AVX512f version

Initial fix of attribute ‘target(default)’ is not valid

2nd fix of attribute ‘target(default)’ is not valid

3rd fix by moving pad_parameters into quantizer

Revise Quantizer by adding commoh.hpp

fix typo in default quantizer

Revise FeatVec_T and Quantizer #centroids

revise quantizer train, and some other minor fixes

add some comments on variables

add type checker

pecos/core/ann/hnsw.hpp

@@ -246,7 +246,6 @@ namespace ann {
     template<class FeatVec_T>
     struct GraphProductQuantizer4Bits : GraphBase {
         typedef FeatVec_T feat_vec_t;
-
         ProductQuantizer4Bits quantizer;
         index_type num_node;
         // code_dimension is number of 4 bits code used to encode a data point in GraphPQ4Bits