(FatalConversionError.conv): add style

(FatalConversionError.conv): add style
covnersion rule.

* scm/chord-name.scm (set-chord-name-style): new function.
(new-chord-name-brew-molecule): revise to interpret markup only
(new-chord->markup): cleanuppish rewrite. To be called from the
new engraver.

* lily/new-chord-name-engraver.cc: new engraver: call Chord ->
Markup earlier, during interpreting.

* input/test/{banter,jazz,american}-chords.ly (scheme): update
style settings. Rename to chord-names-*.ly