Fix Unitframe Taint

Interface Options Skin Removed
(http://us.battle.net/wow/en/forum/topic/6607331970#10)
Skinning Module Updates

CharacterFrame redesigned
Fixed FrameLevel on "Apply" button for VideoOptionsFrame
Modified Skada skin when chat background is disabled
FriendsFrame now skinned
Misc Cleanup

S.borderinset variable now available. Accessing a variable is more
efficient than calling S.GetBorderInset
BNToastFrame now anchors properly
TrimIcon function now available for more convenient and customizable
icon trimming.
SkinEditBox function now available
Gloss texture now more apparent
SkinButton will no longer return an error if the button does not have a
global name
SkinDropDown function improved
SkinScrollBar modified in order to keep templates more consistent in
style when skinned