A fully working version of the scheduling language with added examples

examples/petrinet/petrinet_renderer.j2

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+digraph G {
+  rankdir=LR;
+  center=true;
+  margin=1;
+  nodesep=1;
+  subgraph places {
+    node [fontname=Arial,fontsize=10,shape=circle,fixedsize=true,label="", height=.35,width=.35];
+    {% for place in places %}
+      {{ place[0] }} [label="{{ place[1] }}_{{ place[2] }}"]
+    {% endfor %}
+  }
+}