Media notifications currently always show the forward and backward
buttons as clickable, regardless of whether the corresponding action
is available or not. Media players usually address this by rendering
controls insensitive in this case, so do the same here.
https://bugzilla.gnome.org/show_bug.cgi?id=773884
The section titles usually don't provide a lot of value - messages
themselves are usually pretty unambiguous about their type, and
having a hidden shortcut to some settings panel or application isn't
essential either - except when showing the selected date when browsing
other days, as it adds context to the listed events. Based on that,
remove the section title as a general MessageListSection feature and
move it into the EventsSection, where we only show it when it is useful.
https://bugzilla.gnome.org/show_bug.cgi?id=775763
We lost media controls outside of notification banners when
implementing the new notification designs. Reimplement this
functionality as a dedicated "Media" section in the message
list based on MPRIS.
https://bugzilla.gnome.org/show_bug.cgi?id=756491
