Print combined run time after finishing all shell unit tests
Ignore invalid gradients instead of drawing fully opaque white

I'm not entirely sure why I thought this was the correct behavior in the first place. Flash just ignores the `beginGradientFill`/`lineGradientStyle` call and continues using whatever was specified before.
Fix bugs in Graphics#lineGradientStyle and add unit test
Implement emitting line gradient definitions in defineShape
Implement rendering line gradients
Merge pull request #1370 from tschneidereit/nat

Support for line gradients in embedded shapes and via Graphics API commands