fix #36366: parse verse number, left align to syllable

As discussed in issue and in https://github.com/musescore/MuseScore/pull/1322, it is desirable to move away from separate Verse Number elements and toward a scheme where we automatically process leading verse numbers in lyric syllables.  This PR implements such a scheme.  If a lyric of the form

digits (optional separators) word

then the digits are taken to be a verse number, and the lyric is left aligned at the start of the word.  A lyric consisting of digits *only* is not affected, so you can use numbers as lyrics with no problems.

I also elected to address http://musescore.org/en/node/24856 - ignoring leading punctuation - since it was easy to deal with both leading digitas and leading punctuation at the same time.  Leading punctuation is ignored when positioning lyrics just as leading digits are, but the syllable is still centered.

I also fixed an issue where if you explicitly set the lyric style to left aligned, bad things happened with melisma.  Again, I was modifying this code anyhow, this fix came for free.