Moved 3 box-offset-* tests in their more appropriate
visuren/ folder along with their associated
reference files accordingly.

--HG--
rename : css21/box-offsets-abs-pos-001.xht => css21/visuren/box-offsets-abs-pos-001.xht
rename : css21/box-offsets-rel-pos-001.xht => css21/visuren/box-offsets-rel-pos-001.xht
rename : css21/reference/box-offsets-rel-pos-002-ref.xht => css21/visuren/box-offsets-rel-pos-002-ref.xht
rename : css21/box-offsets-rel-pos-002.xht => css21/visuren/box-offsets-rel-pos-002.xht
rename : css21/backgrounds/support/100x100-lime.png => css21/visuren/support/100x100-lime.png
rename : css21/backgrounds/support/100x100-red.png => css21/visuren/support/100x100-red.png
rename : css21/support/green_box.png => css21/visuren/support/green_box.png