Allow validating media files and deleting additional OS files

[hyeeyoungkim]

This pull request includes:

• New: check_output_structure.py can validate audio (.wav) and video (.mp4) files using FFmpeg's -f null method
• New: check_os_files.py (previously check_thumbs_db_ds_store.py) can target additional operating system files, Desktop DB and Desktop DF
• Improvement: check_output_structure.py and check_os_files.py includes additional parameters to turn off functions
• Improvement: check_output_structure.py provides an execution time message
• Improvement: check_os_files.py asks for user's confirmation before deleting files
• Various bug fixes

README.md has been also updated to reflect the changes. The scripts have been tested with large CD-based accessions on Windows, Python 3.7.2.

[djpillen]

Just to make sure we're following standard conventions and that we don't run into any issues adding additional parameters in the future, would it be possible to make sure that all arguments follow the GNU Program Argument Syntax Conventions for the use of single/double hyphens for short (i.e., single character) and long options? Some of the arguments as they are currently formulated could be interpreted as multiple short options, e.g. -src could be read as equivalent to -s -r -c, -ds could be read as equivalent to -d -s, etc.

[hyeeyoungkim]

@djpillen Thanks for pointing out the parameter issue. I'll check the convention document and update the parameters.

[hyeeyoungkim]

@djpillen I updated argparse argument names for all scripts.

[djpillen]

Looks good, thanks!