Progress: Continue working on completing the remove program.

Progress: Continue working on completing the remove program.

Update the copyright year.

Add the `unlink` program.
Make sure all necessary callbacks are available to perform this.
Use a custom parameter processing to more closely match the standard Coreutils unlink argument.
I am still preserving some of the core parameters of the FLL/Kevux projects.
(This means that there is the `++version` and the `--version`.)

Fix bug where no error was being printed on non-existent file.
Make sure to also exit on error in this situation.