[1.1] General Style dlg box disallows neg. values for lyrics margins

Setup: SVN rev. 4569; Qt Lib 4.7.3; Win XP

Description: Menu "Style | General Style" tab "Page": the boxes for "Lyrics upper margin" and "Lyrics lower margin" do not accept negative values.

Rationale: Even with both lyrics margins set to 0.0, if lyrics are present, the actual distance between staves is never less than ca. 10 spatium (see this forum bug report for additional data).

This may be fine for scores with few vocal staves, but for (large) choir scores makes impossible to place the lyrics when needed / wanted with respect to the above and below staves, with an efficient usage of the space.

Allowing negative margin values for lyrics would make possible any vertical spacing of staves and lyrics for the most efficient usage of sheet real estate.

Note: The supplied patch only changes the dlg box definition (file editstyle.ui), allowing negative values for lyrics margins to be entered (down to -100.00); no change is needed to code.

(The patch is large because SVN diff seems to do a poor job diff-ing .ui files; actually only the properties of those two edit boxes are changed.)

Alpha-tested with several scores.