New helper method for changing the picture path in a .pickle file
Changing tree method to get_hyponyms_trees_with_filenames frontend.py

In order to get frontend.py (and pipeline.py) running, the synset_filenames_dict.pickle has to be stored in the frontend folder.You can change the picture path in the current synset_filenames_dict_x.pickle to your own path, using the helper rename_paths_in_pickle.py
Refactor main in pipeline.py that get_hyponyms_trees_with_filenames can be called from another file.