Git: Save settings

VCSBaseClient handles saving of settings for us, but we do not
use that yet, so we have to do that ourselves:-(

Change-Id: I731d01d429497581fad814effd68bbd784e05fe8
Reviewed-on: http://codereview.qt-project.org/6080
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/git/gitclient.h

@@ -229,6 +229,7 @@ public:
 
 public slots:
     void show(const QString &source, const QString &id, const QStringList &args = QStringList());
+    void saveSettings();
 
 private slots:
     void slotBlameRevisionRequested(const QString &source, QString change, int lineNumber);