Added config entries for thread downloading.
Accomodated the thread downloading config options in parseconf.py
Additional config file parser output parameter for downloading threads.
Specify that it's required to set "downloadhtml" if one wants to download any other part of a thread.
Add strip_invalid_filename_chars(filename) to utils.
delete_files_in_dir(directory_path) should be more memory-efficient.
strip_invalid_filename_chars(filename) should allow unicode characters properly.
Syntax error in delete_files_in_dir(directory_path).
Add missing format argument in pretty_date_delta(time).
Minor punctuation change.
Initial thread downloading support, html only.