Add Model section

tex/3_mod/7_models/1_intro.tex

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+\subsection{Forecasting Models}
+\label{models}
+
+This sub-section describes the concrete models in our study.
+Figure \ref{f:inputs} shows how we classify them into four families with
+    regard to the type of the time series, horizontal or vertical, and the
+    moment at which a model is trained:
+Solid lines indicate that the corresponding time steps lie before the
+    training, and dotted lines show the time horizon predicted by a model.
+For conciseness, we only show the forecasts for one test day.
+The setup is the same for each inner validation day.
+
+\
+
+\begin{center}
+\captionof{figure}{Classification of the models by input type and training
+                   moment}
+\label{f:inputs}
+\includegraphics[width=.95\linewidth]{static/model_inputs_gray.png}
+\end{center}