properties: Use template to create BaconVideoWidgetProperties

So this is the properties window created in a proper way with a template.

I used a GtkDialog as a parent class instead of HdyWindow because it has the escape shortcut (I don't know if it's a valid reason).

Also, the property name for title is media-title to avoid conflict with the title property of GtkDialog...

I did this way as to avoid as much as possible heavy changes. Please let me know if you're not okay with it.

Thanks