Remove original images after blurring

[Frezs19]

This PR add a function and an argument to remove original images after blurring process. The parameter is set to False by default.

[mdraw]

If you are just dealing with images and not videos, you can overwrite the input files by supplying the input file path as the -o argument.

For example:

$ deface city.jpg -o city.jpg

The original city.jpg is then replaced by the anonymized version, so no deletion is required for the same effect. This does not work with folder inputs but for example you can process all .jpg files in a folder by writing a for loop in bash:

$ for f in *.jpg; do deface "$f" -o "$f"; done