VCS: Refresh submit editor status when it might change

Including Git implementation

Task-number: QTCREATORBUG-5644

Change-Id: Ic5dede99d93b84e5d271292b4694216f51e66882
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/vcsbase/submitfilemodel.h

@@ -62,6 +62,7 @@ public:
     QString state(int row) const;
     QString file(int row) const;
     bool checked(int row) const;
+    void setChecked(int row, bool check);
     QVariant extraData(int row) const;
 
     bool hasCheckedFiles() const;