Bugfix: Fix handling of --line when not using --whole.

Bugfix: Fix handling of --line when not using --whole.

The function `iki_read_process_at()` is incorrectly named and should instead be called `iki_read_process_line()`.

The `--object`, `--content`, and `--literal` parameters with `--line` should print the line number for the output of those commands raather than the output of the file.
The printing of the line from the original file is very confusing and so I am considering this a bug.

Update the print help message.