Merge pull request #4006 from aws-lumberyard-dev/Atom/santora/UseLibPng
OpenImageIO is a huge library and overkill for Atom's needs, which is to just save and load png files at this time. Here we remove all dependence on OpenImageIO and use libpng instead. I introduced a PngFile wrapper class to assist with loading and saving png files.
Note that there is a bit more work to do before merging these changes. I am still working on adding libpng to the 3rdParty package system. Currently these changes only reflect the addition of the Windows package. We'll make the other platform packages available before merging.
santorac
f765dc0942