Activating ImageIOImage for reading PNG images in the ImageFactory made some test...

Activating ImageIOImage for reading PNG images in the ImageFactory made some test cases fail. The reason is that the PNGReader cannot extract the image resolution and leaves the default of 72dpi.
Added code to inspect the image metadata for resolution info.
I added the same hack as is already used in PNGImage to force loading the whole image when the image dimensions are requested, i.e. getting the right image size is more important than efficient memory use for now.
The image package needs that redesign sooner or later....

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@425178 13f79535-47bb-0310-9956-ffa450edef68