Modified some figures

Signed-off-by: Riccardo Finotello <riccardo.finotello@gmail.com>

sec/part1/dbranes.tex

@@ -81,15 +81,13 @@ We thus choose $X_{(t)}^1$ and $X_{(t)}^2$ to be the coordinates parallel to the
   \centering
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{branesangles.pdf_tex}
+    \import{tikz}{branesangles.pgf}
     \caption{D-branes as lines on $\R^2$.}
   \end{subfigure}
   \hfill
   \begin{subfigure}[b]{0.45\linewidth}
     \centering
-    \def\svgwidth{\linewidth}
-    \import{img}{welladapted.pdf_tex}
+    \import{tikz}{welladapted.pgf}
     \caption{Well adapted system of coordinates.}
   \end{subfigure}
   \caption{%