Storage format
Now import_config function in storage.py returns a dictionary instead of an option file
Config files corrections

allowed_file_extensions in trackers/sample.config are now comma separated (aesthetics...), file_download_level none value renamed to disabled, for avoiding confusions with Python None, op_words variable changed to lowercase. Now all config parameters will go lowercase, and sections will go uppercase, to avoid users confusions when modifying these files.

log_level at config/default.config set to verbose for future debugging