Using the XPM format for images has become a maintenance problem because
people don't know how to create them. This commit removes all XPM images
and all C files that contain PNG images. DolphinWX now uses the PNGs
in the Resources folder instead, just like DolphinQt and DolphinQt2 do.
fileplatform is moved so it's in the same place as the other platform
icons, and nobanner is moved just because it fits better in Resources.
Both of them were identical in all of Dolphin's themes.
JosJuice