Implement "listen" command

This command will connect to all signals from Solid::Power and reprot
any change that is detected in the system.

src/tools/solid-power/main.cpp

@@ -67,5 +67,11 @@ int main(int argc, char **argv)
 
     if (command == QLatin1String("show")) {
         power.show();
+    } else if(command == QLatin1String("listen")) {
+        sOut << "Listening to events:" << endl;
+        power.listen();
+        app.exec();
+    } else {
+        sOut << "Not recognized command" << endl;
     }
 }
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src/tools/solid-power/solid-power.cpp

@@ -44,4 +44,15 @@ void SolidPower::show()
     QString status = job->isPlugged() ? "yes" : "no";
 
     sCout << "is AC plugged:\t" << status << endl;
+}
+
+void SolidPower::listen()
+{
+    auto power = Power::self();
+
+    connect(power, &Power::acPluggedChanged, [](bool plugged){
+        QTextStream lOut(stdout);
+        QString status = plugged ? "yes" : "no";
+        lOut << "\tAC plugged changed:\t" << status << endl;
+    });
 }
\ No newline at end of file

src/tools/solid-power/solid-power.h

@@ -31,6 +31,7 @@ public:
     explicit SolidPower(QObject *parent = 0);
 
     void show();
+    void listen();
 };
 
 #endif //SOLID_POWER_TOOL_H
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