update lyrics style settings (position/margins)

As per http://musescore.org/en/node/25247#comment-116851, the new default settings are:

- text style vertical position: 6sp (which is what the *actual* default was for 1.3, even though style said 7sp)
- lyric upper margin: 2.0sp
- lyric lower margin: 4.0sp

This will result in lyrics being positioned in same place vertically as in 1.3, but by default there will be not quite as much space reserved below the lyrics as in 1.3 (this is a good thing).  1.3 scores will continue to have the same spacing.

The vtest attached, btw, is using the new default lyric bottom margin,  but it increases the upper margin to clear the downstem notes.  That was necessary in 1.3 for scores in this format and will remain so.