Add style support to display capo chords only

[hoongern]

Feature proposal: Add a new style option to "display capo chords only". When enabled, chord readability and layout improves (on scores with a dense number of chords), for parts/musicians which only care about the capo chords.

E.g. When enabled with capo fret 1, "Am7/C" would be displayed instead of "Bbm7/Db (Am7/C)".

Given the desired flexibility for some parts to display capo chords, other parts to display both original & capo chords, and to be synced, it seemed easier to write this into the core harmony code rather than using a plugin (although I do not have experience with the codebase and am open to other suggestions on how to achieve this effect). This does seem to mean that saving the score in a build missing the style id erases the option.

If this approach seems reasonable, I could look into writing a test (I couldn't find documentation on running unit tests on Mac OS). I've performed a simple manual test with a mix of chord symbols, nashville chords and roman numerals.

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