Modify PacedTimingFunction to operate over a range

This will be required to implement chained timing functions.
Update generated results for auto-test-timing-functions.html

Use a larger movement and the new generated results style. This will reduce
noise when the test is expanded for chained timing functions.

No functional change.
Implement chained timing functions

These are specified through the following attributes on Timing ...
- easing: A space-separated list of timing functions
- easingPoints: A space-separated list of the end points of the input/output
  ranges over which the timing functions apply. The following keywords are also
  allowed ...
  - distribute: Distribute timing functions evenly in time.
  - align: If the TimedItem with which this Timing object is associated is an
    Animation with a keyframe or path effect, align timing functions with
    keyframes.

See http://dev.w3.org/fxtf/web-animations/#timing-function-chains for details.

Note that alignment with a path effect is not yet implemented.