Implemented "Add Existing Directory..." feature.

This feature lets add files from selected directory and its
subdirectories to project. Files to add are selected based on filter
supplied by a user.

Task-number: QTCREATORBUG-9081
Change-Id: I978e87c24c5aeffc4eb74160cd6f4f20096de017
Reviewed-by: Daniel Teske <daniel.teske@digia.com>

src/plugins/genericprojectmanager/filesselectionwizardpage.h

@@ -39,11 +39,14 @@ class QTreeView;
 class QLineEdit;
 QT_END_NAMESPACE
 
+namespace ProjectExplorer {
+    class SelectableFilesModel;
+}
+
 namespace GenericProjectManager {
 namespace Internal {
 
 class GenericProjectWizardDialog;
-class SelectableFilesModel;
 
 class FilesSelectionWizardPage : public QWizardPage
 {
@@ -68,7 +71,7 @@ private:
     void createApplyButton(QVBoxLayout *layout);
 
     GenericProjectWizardDialog *m_genericProjectWizardDialog;
-    SelectableFilesModel *m_model;
+    ProjectExplorer::SelectableFilesModel *m_model;
 
     QLabel *m_hideFilesFilterLabel;
     QLineEdit *m_hideFilesfilterLineEdit;