Move window restoration code to main Loading sub

This way, if images are loaded from the command line, the main form will
already be in the proper place instead of leaping across the screen
after the images are loaded.
Much more stability for loading EXR images with alpha

They may not always load correctly, but that's a FreeImage problem - not
a PhotoDemon one.

Also, unsupported EXR types will no longer crash the program.