[1.0] musicxml import: voices mixed up

When importing MusicXML, the voice mapper (voicelist) is reset at the start of each measure. This changes the mapping of MusicXML to MuseSCore voice numers if the first notes of each voice are found in the MusicXML file in a different order compared to other measures. End result is that the voices are mixed up: notes in voice x may be in voice y in another measure.