display-toolbar: Minor indentation fix

https://bugzilla.gnome.org/show_bug.cgi?id=735329
actions-popover: Switch to collection on deletion

In the following patch, we'd show this popover in display mode too and it
looks really weird if we keep showing the display of the machine that
user just deleted. Better switch to collection view just before deleting
(from view) it.

https://bugzilla.gnome.org/show_bug.cgi?id=735329
display-toolbar: props button -> box menu button

Replace properties button by a menu button that presents the box actions
using the new ActionsPopover.

https://bugzilla.gnome.org/show_bug.cgi?id=735329