clarify in docs that methods taking a size arg deal in pixels, not points

[willbur1984]

for example, KLO_imageByResizingToSize: arg is a size, but it isn't scaled to the screen scale by default, since it deals in pixels. add a note in the docs that indicate the client should use KDICGSizeAdjustedForMainScreenScale when resizing things like icons and rely on the default behavior when resizing something like a content image.