Postprocessing demo

In order to run the demo one needs to execute the following steps:

1. Run csv_generator.py to generate dataframes for query and gallery sets.
2. Run prepare_images_zips.py to generate dataframes for query and gallery that only contains queries for which there were some changes during the postprocessing step, and also zip-file with all the query and gallery images.
3. Run streamlit main.py in order to run the demo.