Add escape as a means of sanitization

[thombashi]

The current sanitization functions replace ineligible characters for file-names/file-paths with the specified string.
Add escape (unescape) as an alternative processing option.

Add an argument like invalid_value_handler to sanitize functions, allowing the user to choose between replace (the current behavior) and escape.
Arguments like replacement_text may be passed as invalid_value_handler_args argument.