Correct the reference.

* it shouldn't show a red rectangle
* the text must be included
Fix css3-transform-scale-002 reference.

* should show a green rectangle
* should include the text (to match test)
Move image files to support/

- Move css-background-3/ images to support/
- Move css-background-3/reference/ images to support/
- Delete duplicated images: yy.png, table-head.jpg in reference/
fixed flexbox spec links to match the new shortname in the spec DB
merging
removed spec and assert metadata from ref files
Remove two unreferenced img files

Deleted support/support/swatch-green.png
Deleted support/support/swatch-red.png
Merge pull request #579 from chenxix/chenxix/csswg-test/move-3-pic

Move image files to support/
merge
Simplify reference.
Simplify reference.
Merge pull request #572 from ed-ed/fix_rotateY

Correct the css3-transform-rotateY reference.
Merge pull request #573 from ed-ed/fix_scale002

Fix css3-transform-scale-002 reference.
Merge pull request #580 from chenxix/chenxix/csswg-test/remove-sub-support

Remove two unreferenced img files