Previously top revealer was set to fixed size, which caused a noticable video tearing along the revealer edge during its animation. This commit removes fixed revealer size, which in turn casues the revealer to cover whole video screen (default behavior), thus eliminates the tearing. Since overlay now becomes the top widget, all player notify signals were reconnected to it.
This adds Kodi-like semi-transparent overlay with current media title, hour and estimated time when video will end. The overlay is visible only on fullscreen mode.
Create volume button with popover instead of using GTK provided volume button.
Creating new button with only needed elements is more efficient then removing unneeded items from pre-made volume button. This should also increase performance a little when changing volume, because now we generate new icon only when a change is needed. In pre-made button icon is regenerated on each volume change.
