main: Don't add containers in the Recent view

Try harder not to add containers to the recent view, we don't
want to see them, and they break navigation (for the bookmarks
source for example).

https://bugzilla.gnome.org/show_bug.cgi?id=726874
opensubtitles: Work-around Find button not having a label

Re-using stock items, which we'll remove after string freeze.
opensubtitles: Fix leading underscore in close button
opensubtitles: Fix error with newer version of PyGObject

We cannot pass an object as user_data, as pygobject stopped handling
non-integers, non-capsules or not None as possible arguments.

As we do not use Totem.plugin_load_interface()'s signal connection
feature, pass None instead.

https://bugzilla.gnome.org/show_bug.cgi?id=724093
all: Revert all totem_set_popover_no_shadow() bits

Since GTK+ commit eb0f86d48, this hack is no longer necessary as
GtkPopover sets invariably a more fitting shape.

https://bugzilla.gnome.org/show_bug.cgi?id=726927
3.12.0