Check/delete open ties that don't exceed measure duration. Currently unused as it's incorrect, see below.
Create new [[VoiceEntry]], add it to given [[SourceStaffEntry]] and if given so, to [[Voice]].
States whether the new VoiceEntry (only) has grace notes
Create [[Note]]s and handle Lyrics, Articulations, Beams, Ties, Slurs, Tuplets.
Software like Guitar Pro gives one octave too low, so we need to add one
whether the note should be rendered (true) or invisible (false)
Create a new [[StaffEntryLink]] and sets the currenstStaffEntry accordingly.