MEISE validation compatibility

Tweaked document header and tie attributes so exported files pass MEISE
validation.
Beginning to support lyrics

<verse> and <syl> tags seem to be in the right places on export, and
the word position data seems to be correct, but I still need to add
code that gets the text inside the <syl> tag.
support for 0,1,2 lines of lyrics

Unfortunately, running the plugin resulted in a parsing error when I
tried to use a global sparse array. So used a rather hackish solution
to get no more than 2 lines of lyrics working. Syllables are exported
as child elements within noteheads, with (hopefully) correct
word-position information.
Dummy commit so I can sync changes?