core: use Core::Id for IVersionControl::id()

Change-Id: I54e17c91c3e2a69d598ed485235dbf7ec62b4615
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/coreplugin/iversioncontrol.h

@@ -34,6 +34,7 @@
 #define IVERSIONCONTROL_H
 
 #include "core_global.h"
+#include "id.h"
 
 #include <QtCore/QObject>
 #include <QtCore/QString>
@@ -64,7 +65,7 @@ public:
     virtual ~IVersionControl() {}
 
     virtual QString displayName() const = 0;
-    virtual QString id() const = 0;
+    virtual Id id() const = 0;
 
     /*!
      * Returns whether files in this directory should be managed with this