Some final tweaks to 'Design' chapter.

docs/data/diagrams.tex

@@ -140,7 +140,7 @@
 }
 
 \def\trackerdiagram{
-    \begin{figure}[h]
+    \begin{figure}[h!]
         \center
         \architecture{
             \node[block, below of=driver] (eventdriver) {Event driver}