Move binarize_features, retrieve_images to examples/feauture_extraction

diff --git a/tools/binarize_features.cpp b/examples/feature_extraction/binarize_features.cpp
similarity index 100%
rename from tools/binarize_features.cpp
rename to examples/feature_extraction/binarize_features.cpp

diff --git a/tools/extra/generate_file_list.py b/examples/feature_extraction/generate_file_list.py
similarity index 100%
rename from tools/extra/generate_file_list.py
rename to examples/feature_extraction/generate_file_list.py

diff --git a/tools/retrieve_images.cpp b/examples/feature_extraction/retrieve_images.cpp
similarity index 100%
rename from tools/retrieve_images.cpp
rename to examples/feature_extraction/retrieve_images.cpp