note regarding preferences in sketch

doc/chapter/3ui.tex

@@ -11,6 +11,7 @@ Figure~\ref{fig:originalpapergraph} compares our results to those of Brandes and
     \includegraphics[width=\linewidth]{img/skizze}
     \caption[First sketch of the planned layout]{A first sketch of the planned layout, created with Microsoft Paint.
     The buttons are (first row, from left to right): step over, step into, step out, run, pause, debug; and (second row, from left to right): step back over, step back into, step back out, run backwards, load graph, save graph, generate random graph.
+    Currently a button to open the preferences dialog is located in the second row at the empty position.
     The actions corresponding to the buttons are the same as described for the keyboard input in table~\ref{table:keys}, at least for the features that are already implemented (all of them).
     The left four rectangles show the progress of the four extremal layouts.
     The right rectangle shows pseudocode of the algorithm and the position of the current step.}