Add missing forward declaration
Replace using statement with full qualification
for class member definitions
Replace algorithm header with utility header
Refactor resolution from video to free function
Set window title in video loaded slot

Move duplicate setWindowTitle calls from member functions where
a loadFile() is called and the absolute path to the opened file
is set in the config file to videoLoaded() slot
Set last opened video file to config in loadFile()

Move all the duplicate config.setValue() calls from member functions
where loadFile() is called to loadFile()
Refactor avinfoParseVideoHeader free function