Add initial version of volume control

Signed-off-by: Piotr Galiszewski <pgaliszewski@corp.bluecherry.net>
Fix unnecessary double video reseting when changing video event

Signed-off-by: Piotr Galiszewski <pgaliszewski@corp.bluecherry.net>
Remember audio settings between different videos

Signed-off-by: Piotr Galiszewski <pgaliszewski@corp.bluecherry.net>