Add test suite and benchmark.

.clang-format

.vscode/settings.json

ppann/Makefile

ppann/benchmark/benchmark-ipre.cpp

ppann/include/asym-field.hpp

ppann/include/asym_field.hpp

ppann/include/hnsw.hpp

ppann/include/ipre.hpp

ppann/include/sym-field.hpp

ppann/src/asym-field.cpp

ppann/src/helper.cpp

ppann/src/hnsw.cpp

ppann/src/ipre.cpp

ppann/src/sym-field.cpp

ppann/src/sym-matrix.cpp

ppann/src/sym-vector.cpp

ppann/test/test-asym-field.cpp

ppann/test/test-asym-group.cpp

ppann/test/test-helper.cpp

ppann/test/test-hnsw.cpp