Core: Allow adding additional information to about dialog.

Purpose is to get rid of hard coded license information string in the Qt
Creator binary.

Change-Id: I867e2aed010f8a622adfbb89ac96dccbc8229161
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/coreplugin/mainwindow.h

@@ -110,6 +110,9 @@ public:
 
     void setOverrideColor(const QColor &color);
 
+    QStringList additionalAboutInformation() const;
+    void appendAboutInformation(const QString &line);
+
 signals:
     void newItemDialogRunningChanged();
 
@@ -152,6 +155,7 @@ private:
     void writeSettings();
 
     ICore *m_coreImpl;
+    QStringList m_aboutInformation;
     Context m_highPrioAdditionalContexts;
     Context m_lowPrioAdditionalContexts;
     SettingsDatabase *m_settingsDatabase;