software/django: Install Django packages

software/django-tutorial/software.cfg

 [buildout]
 extends =
   ../../stack/slapos.cfg
+  ../../component/macros/virtual-env.cfg
+
+parts =
+  django-env
+
+[django-env]
+<= virtual-env-base
+location = ${buildout:directory}/activate
+eggs = Django
 
 [python]
 part = python3