ProjectExplorer: Introduce DeviceProcessSignalOperation.

Every device can now return a DeviceProcessSignalOperation,
which allows to kill or interrupt processes running on the
device.

Change-Id: Idaa04ebc767e09ca167fa033ed93860b9b81479e
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Reviewed-by: David Kaspar <dkaspar@blackberry.com>
Reviewed-by: hjk <hjk121@nokiamail.com>

src/plugins/android/androiddevice.cpp

@@ -89,6 +89,11 @@ bool AndroidDevice::canAutoDetectPorts() const
     return true;
 }
 
+DeviceProcessSignalOperation::Ptr AndroidDevice::signalOperation() const
+{
+    return DeviceProcessSignalOperation::Ptr();
+}
+
 IDevice::Ptr AndroidDevice::clone() const
 {
     return IDevice::Ptr(new AndroidDevice(*this));