Fixing the generator as discuss in the testing meeting.
Fix MediaReference after switch to new Timing interface

This was broken by 5ee65b94527a1c0808d89f2ba229d88303310332 and following commits.

Also fix the test after the switch to the new testing framework.
Fix MediaReference to stop the media when detached from its Player
Merge pull request #316 from steveblock/mediaRefSubmission

Fix MediaReference after switch to new Timing interface
Implement accumulate for KeyframeAnimationEffect
Merge pull request #335 from steveblock/accumulate

Implement accumulate for KeyframeAnimationEffect
Add a test that applying accumulation takes immediate effect
Merge pull request #342 from steveblock/addAccumulateUpdateTest

Add a test that applying accumulation takes immediate effect
Fix keyframe distribution
Merge pull request #341 from steveblock/fixKeyframeDistribution

Fix keyframe distribution
Merge pull request #337 from mithro/fixing-generator

Fixing generator, third attempt.
Fix assert_styles() to handle negative values
Merge pull request #343 from steveblock/negativeValues

Fix assert_styles() to handle negative values
Fix fromCssValue() methods to return undefined if the input value is invalid

Currently, the various fromCssValue() methods handle bad input differently.
This change standardises the handling so that missing logic is more obvious.

It also adds a console.assert() to the main fromCssValue() function to detect
this condition, and a TODO to fix the keyframe normalization process to ensure
the assert is never hit.
Clean up the fooType classes used for adding and interpolating property values

- Fix some fromCssValue() and interpolate() methods to allow a tests to be
  added for various types of composition.
- Add zero() methods where required and remove some that are superfluous.
- Add TODOs for cases that aren't currently handled.
- Require the arguments to interpolate() to always be provided.
Fixed matrix transform interpolation
Added test and rebased
Merge pull request #346 from alancutter/fixTransformMatrixInterpolation

Fix matrix transform interpolation
Alert you about trying to generate without loading testharness_timing.
Fixing the testharness to work when there are no tests.

Fixes #347.