Remove ImageDecodingCache debug messages
Fix opening individual images from commandline

ViewLoader would only update when the current file changes after
it has been created; if started from commandline with a specific
file, the file is already set before ViewLoader is instantiated.
Fix a crash with fullscreen menu hiding on Linux

I'm not positive of the reason for this, but I suspect it's
related to non-child widgets and the mapTo call, resulting in
a crash under QWidget::mapToParent.
Display ViewLoader items immediately, even if not yet loaded

As nice of an idea as it is to avoid any flicker on short changes,
it's just not responsive enough.