Improvement: coloring improvements, and remove echo-error

[balupton]

I won't have time for this, however I would welcome someone to do a PR for it.

• ensure all background and foreground color combinations are suitable for color-blind people
• check if there are styles being invoked that are missing
  • perhaps echo-style can write to a $DOROTHY/state/warnings.txt file, that is dumped when new terminals are open; this can also be used for deprecations
• provide good2, notice2, neutral2, error2 styles; consider removing good, successful, negative styles
  • the thing with these numbered styles, is they need a corresponding --code-BLAH= style, and underlines can't be used as the numbered styles include trailing spaces, e.g. --error2='this path is missing: ' --code-error2='a missing path'
• consider redoing confirm (from WIP: ask, choose, confirm: better support no-TTY mode #254) with styles.bash rather than echo-style calls