Fine-tune the autospeller

[stephband]

It is mis-spelling many things, and it needs to be adjusted to make better decisions. From @csterritt:

"
From the "Dolphin Dance" demonstration file, at bar 26:

In the source, the chords are F# and B (in the json, they're chords 100 and 102). However, Scribe (evidently) feels they'd be better shown as "Gb" and "Cb". These chords are not changed (e.g., F# in bar 8 and C in bars 1, etc.). They should not be changed.
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