Plugin: add note names below the chords

Hi *,

this (explicitly note names with octaves in scientific pitch notation, not localised names, for which a plugin already exists) was requested by a user in IRC, so I thought I’d try my hands at a plugin.

Much cursing and reimplementing of core functionality (such as barbeats, for debugging) later I had something that could iterate over and debug things.

Many crashes later I found out that, just maybe, I should upgrade from 3.2.3 to something newer before doing this with lyrics, so I copied it aside and made a version that does it as staff text.

https://github.com/mirabilos/mscore-plugins/blob/master/notenames-as-st…

My first plugin. Enjoy! (I very much did not enjoy JavaScript.)

Feedback welcome, both constructive and snarky, other than any comment related to the MuseScore version in use.