Sometimes pedals are imported that begin or end on segments that have
notes on tracks (or staves) other than the track the spanner is on.
Previously, this would cause incorrect tick adjustments on "change"
type pedals, and it would result in some pedals not being able to
compute a start or end element. This commit fixes these issues by
considering all tracks of a part when assessing pedal change tick
adjustments and when computing start elements.

MusicXML exporters tend to have a fixed maximum <divisions> value,
meaning more complex tuplets (5's, 7's) have incorrect duration values.
These were already handled for tuplets, but sometimes not handled for
<backup> elements within or after a tuplet.

This commit adds a more thorough system for rounding durations off to
more sensible values. In doing so, it unifies the conversion process
from <duration> to Fraction (which previously existed almost identically
in three separate places) to pass1.calcTicks().

Previously, the <offset> element was not correctly applied to any
spanners in <direction> elements. This commit fixes that and adjusts the
applicable tests accordingly.