Allow more shortcuts to bind to one action

[TomasHnyk]

Use case is clear: sometimes one would like to define a custom shortcut but does not want to lose the default one (some shortcuts can be easier to launch with one hand, for example). Also, it could trivially solve issues like this bug 954797.

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: compiz 1:0.9.8.4+bzr3407-0ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-22.34-generic 3.5.7.2
Uname: Linux 3.5.0-22-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.6.1-0ubuntu6
Architecture: amd64
CompizPlugins: [core,composite,opengl,decor,grid,imgpng,compiztoolbox,gnomecompat,mousepoll,resize,snap,regex,place,vpswitch,move,winrules,animation,wall,session,workarounds,expo,fade,scale,ezoom,unityshell]
CompositorRunning: compiz
Date: Sat Feb 2 00:30:48 2013
DistUpgraded: Fresh install
DistroCodename: quantal
DistroVariant: ubuntu
EcryptfsInUse: Yes
GraphicsCard:
 Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:2114]
   Subsystem: Lenovo Device [17aa:2114]
InstallationDate: Installed on 2012-11-26 (67 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MachineType: LENOVO 20828VG
MarkForUpload: True
PackageArchitecture: all
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.5.0-22-generic root=UUID=82c659c7-c1e8-4750-b06c-7f51f0f73878 ro quiet splash vt.handoff=7
SourcePackage: compiz
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/13/2009
dmi.bios.vendor: LENOVO
dmi.bios.version: 7VET64WW (2.12 )
dmi.board.name: 20828VG
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr7VET64WW(2.12):bd03/13/2009:svnLENOVO:pn20828VG:pvrThinkPadT500:rvnLENOVO:rn20828VG:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 20828VG
dmi.product.version: ThinkPad T500
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.8.4+bzr3407-0ubuntu1
version.ia32-libs: ia32-libs 20090808ubuntu36
version.libdrm2: libdrm2 2.4.39-0ubuntu1
version.libgl1-mesa-dri: libgl1-mesa-dri 9.0-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 9.0-0ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.13.0-0ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.7.3-0ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:6.99.99~git20120913.8637f772-0ubuntu1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.20.9-0ubuntu2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.2-0ubuntu3