Shift+Ctrl+X for advanced users that likes to customize the image

- Adds "hidden" shift+ctrl+X shortcut for eXpert image customization
  options.

Allows one to set certain options on RPI OS images, namely:

* disable overscan
* set hostname
* enable ssh and
  - set Pi user password if using password authentication
  OR
  - set authorized_keys
    (if running Imager on Linux/Mac this will
     have contents of ~/.ssh/id_rsa.pub prefilled)
* configure wifi settings
  (if computer running Imager is connected by wifi it will
  prefill wifi SSID and if on Windows also PSK).
* set time zone and keyboard layout

  Related to feature requests/issues:
  Ref #127
  Ref #86
  Ref #102
  Ref #73
  Ref #68
  Ref #25
  Ref #12

- Option Window also allows setting a couple other general settings:

* Adds option for audible notification (beep) when imaging completes.
  Closes #46

* Adds option not to eject media when done.
  Closes #144

- No longer suspends a number of Windows services during Imaging
  (We want Windows to detect the drive and mount it, or we may
   not be able to alter files on FAT partition).

linux/udisks2api.cpp

@@ -170,3 +170,40 @@ bool UDisks2Api::formatDrive(const QString &device, bool mountAfterwards)
 
     return true;
 }
+
+QString UDisks2Api::mountDevice(const QString &device)
+{
+    QString devpath = _resolveDevice(device);
+    if (devpath.isEmpty())
+        return QString();
+
+    QDBusInterface filesystem("org.freedesktop.UDisks2", devpath,
+                              "org.freedesktop.UDisks2.Filesystem", QDBusConnection::systemBus());
+    QVariantMap mountOptions;
+
+    for (int attempt = 0; attempt < 10; attempt++)
+    {
+        qDebug() << "Mounting partition";
+        QDBusReply<QString> mp = filesystem.call("Mount", mountOptions);
+
+        if (mp.isValid())
+        {
+            qDebug() << "Mounted file system at:" << mp;
+            return mp;
+        }
+
+        QThread::sleep(1);
+    }
+
+    qDebug() << "Failed to mount file system.";
+    return QString();
+}
+
+void UDisks2Api::unmountDrive(const QString &device)
+{
+    QString devpath = _resolveDevice(device);
+    if (devpath.isEmpty())
+        return;
+
+    _unmountDrive(devpath);
+}