main: Don't show buttons on show-all
backend: Rework popup visibility

When using the mouse, show the popup on motion, and hide it
after 3 seconds (unless it's on our popup).
When using a touchscreen, show/hide the popup on tap.

https://bugzilla.gnome.org/show_bug.cgi?id=697897
main: Show fullscreen toolbar

When the video widget tells us to show the controls, pop out the
fullscreen toolbar.

Helps: https://bugzilla.gnome.org/show_bug.cgi?id=697897