Time sigs: update glyphs and UI to SMuFL

Updates, completes and partially re-orders code and UI for time sigs in accordance with move to  SMuFL.

1) CODE - New glyphs registered for time sigs added to mscore font.

Now time sigs numerator and denominator accept and properly format '+', '(' and ')' in addition to digits:
- glyphs for '+', '(' and ')' registered for time sigs. added to MScore (in the same code points as SMuFL)
- glyphs for prolationes defined in SMuFL added to MScore registered for time sigs. (in the same code ponts as SMuFL; some existed, but in different code points)
- transcoding ASCII -> SMuFL for '+', '(' and ')' added to Element::toTimeSigString()

2) UI - Reworked the Time Sig Properties dialogue box:

- Restricts accepted characters for time sig. numerator and denominator to '+', '(', ')' and 0-9.
- Replaced "Common time" and "Alla breve" strings with corresponding symbols.
- Added another appearance case with less used time sig symbols for Medieval and Renaissance prolations.
- Changed layout of dlg box (top part) into a 2-column layout, separating value data to appearance data.
- Musical symbols in the dlg box use icons, as the score font glyphs were not suitable due to score-specific registration (11 icons added).

Also:

- Fixed calculation of TimeSig bounding box, which also fixes horiz. alignment of numerator and denominator with different width (bbox was not scaled according to spatium).