partial fix for #25390 - layout of "imported" 1.3 scores

I have implemented the following strategy:

- strip off all manual adjustments for notes, chords, accidentals, and articulations
- for rests, keep vertical adjustments only
- for ties, strip off manual adjustments if there is only a single segment
- apply an overall 5% to measure spacing to attempt to fit as many measures per line as before

It's not perfect, but it's a reasonable starting place for import.

Eventually I would like to preserve manual adjustments in voices 3 & 4 so the slight offsets than are commonly applied to separate them from voices 1 & 2 will be honored.  But then we would need to re-calculate accidental positions as well (see http://musescore.org/en/node/25648).

Handling of unisons - both within a single voice and between voices - is different enough between 1.3 and 2.0 that this will probably be the biggest source of noticeable differences in layout aside from number-of-measures-per-system issues.  But preserving manual adjustments does not work well either, since default positions are different.