Add quit cli command and app quit option after stream session. Fixes #92 (#138)

* Add quit cli command and app quit option after stream session. Fixes #92

* Code review fixes.

app/backend/computerseeker.h

@@ -0,0 +1,33 @@
+#pragma once
+
+#include <QObject>
+
+class ComputerManager;
+class NvComputer;
+class QTimer;
+
+class ComputerSeeker : public QObject
+{
+    Q_OBJECT
+public:
+    explicit ComputerSeeker(ComputerManager *manager, QString computerName, QObject *parent = nullptr);
+
+    void start(int timeout);
+
+signals:
+    void computerFound(NvComputer *computer);
+    void errorTimeout();
+
+private slots:
+    void onComputerUpdated(NvComputer *computer);
+    void onTimeout();
+
+private:
+    bool matchComputer(NvComputer *computer) const;
+    bool isOnline(NvComputer *computer) const;
+
+private:
+    ComputerManager *m_ComputerManager;
+    QString m_ComputerName;
+    QTimer *m_TimeoutTimer;
+};