[bugfix] Make handbook compile again

doc/handbook/1_introduction.tex

@@ -25,7 +25,7 @@ libraries\footnote{In fact, the performance penalty resulting from the
 use of \Dune's grid interface is usually negligible~\cite{BURRI2006}.}.
 \begin{figure}[hbt]
   \centering
-  \includegraphics[width=.5\linewidth, keepaspectratio]{PNG/dunedesign.png}
+  \includegraphics[width=.5\linewidth, keepaspectratio]{png/dunedesign.png}
   \caption{
     \label{fig:dune-design}
     A high-level overview of \Dune's design is available on the project's

doc/handbook/5_models.tex

@@ -140,7 +140,7 @@ As an example, if two equal volumes of gas A and gas B are mixed, the volume of
 %
 \begin{figure}[ht]
 	\centering
-	\includegraphics[width=0.7\textwidth]{PNG/dalton1.png}
+	\includegraphics[width=0.7\textwidth]{png/dalton1.png}
 	\caption{Dalton's law visualized}
 	\label{fig:dalton1}
 \end{figure}
@@ -166,7 +166,7 @@ As an example, if two volumes of gas A and B at equal pressure are mixed, the pr
 %
 \begin{figure}[ht]
 	\centering
-	\includegraphics[width=0.7\textwidth]{PNG/dalton2.png}
+	\includegraphics[width=0.7\textwidth]{png/dalton2.png}
 	\caption{Amagat's law visualized}
 	\label{fig:dalton2}
 \end{figure}

doc/handbook/5_spatialdiscretizations.tex

@@ -18,7 +18,7 @@ by connecting the midpoints and barycenters of the elements surrounding node
 $i$ creating a box $B_i$ around node $i$ (see Figure \ref{pc:box}a).
 
 \begin{figure} [ht]
-\includegraphics[width=0.8\linewidth,keepaspectratio]{PNG/box_disc.png}
+\includegraphics[width=0.8\linewidth,keepaspectratio]{png/box_disc.png}
 \caption{\label{pc:box} Discretization of the box method}
 \end{figure}
 
@@ -179,7 +179,7 @@ flow and transport equations:
 
 \begin{figure} [ht]
 \centering
-\includegraphics[width=0.4\linewidth,keepaspectratio]{PNG/cc_disc.png}
+\includegraphics[width=0.4\linewidth,keepaspectratio]{png/cc_disc.png}
 \caption{\label{pc:cc} Discretization of the cell centered finite volume method}
 \end{figure}
 

doc/handbook/CMakeLists.txt

@@ -21,13 +21,13 @@ set(TEX_INPUTS
   installDumux.sh)
 
 set(TEX_IMAGES
-  PNG/box_disc.png
-  PNG/cc_disc.png
-  PNG/dumux_strucutre_flowchart_horizontal_explained.png
-  PNG/dunedesign.png
+  png/box_disc.png
+  png/cc_disc.png
+  png/dumux_strucutre_flowchart_horizontal_explained.png
+  png/dunedesign.png
   ../logo/dumux_logo_hires_whitebg.png
-  PNG/dalton1.png
-  PNG/dalton2.png)
+  png/dalton1.png
+  png/dalton2.png)
 
 dune_add_latex_document(0_dumux-handbook.tex
   BIBFILES dumux-handbook.bib