Implement special keys to switch option values in interactive mode

With this commit, we can now change option values in interactive mode with the
folowing special keys

- CTRL-L  left_margin
- CTRL-R  right_margin
- CTRL-D  delimiter_align
- CTRL-I  indentation
- CTRL-U  ignore_unmatched
- CTRL-G  ignore_groups

('ignores' option has been renamed to 'ignore_groups', but backward-compatible)