Measure alignment for tempo text and rehearsal marks

This change affects both tempo texts and rehearsal marks, if attached to first chord/rest of measure.

For tempo text, the text is aligned normally unless there is a time signature earlier in the bar - in which case, it aligns with that.

For rehearsal marks, the text aligns with the start of the measure (over the barline).

In both cases, new and 1.3 scores will pick up up the change automatically.  For 1.3 scores, any user offset that had been applied is rebased on first layout.