add a confirm dialog for "abort all actions" (copy and move actions)

[Karl-Philipp Richter]

It is too easy to abort all transactions of files (move or copy actions) with the menu item "abort all actions" of the nautilus popup menu. Is is aggravated by the fact that the menu item is right above the item "show copy dialog".

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: nautilus 1:3.10.1-0ubuntu15
Uname: Linux 3.16.7-031607-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.14.7-0ubuntu8
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Nov 5 22:47:44 2014
GsettingsChanges: b'org.gnome.nautilus.list-view' b'default-column-order' b"['name', 'size', 'type', 'date_modified', 'date_accessed', 'owner', 'group', 'permissions', 'mime_type', 'where']"
SourcePackage: nautilus
UpgradeStatus: No upgrade log present (probably fresh install)