fix #40066: use es/is for german chords if lower case option enabled

Lots of back and forth on this, but finally everyone seems happy with what we've decided.  For chord symbols in German mode, we will use H & Bb, other accidentals also "b" and "#", *unless* the lwoer case minor chord option is selected.  In that case, we go to a "pure" German mode in which we use B instead of Bb and es/is instead of b/#.  Also, we'll only spell bass notes lower case with this option selected.

It's actually easier supporting it this way than with the handstands that were needed (both in the code and by the user) to have the "pure" mode be a function of the chord definition file only.