add required code to draw database diagram

do not forget to update dependencies.

ippisite/ippisite/settings.py

@@ -37,6 +37,7 @@ INSTALLED_APPS = [
     'django.contrib.sessions',
     'django.contrib.messages',
     'django.contrib.staticfiles',
+    'django_extensions',
     'bootstrap3',
     'ippidb'
 ]
@@ -120,3 +121,12 @@ USE_TZ = True
 # https://docs.djangoproject.com/en/1.10/howto/static-files/
 
 STATIC_URL = '/static/'
+
+# required to use django-extensions to draw database diagram
+# to do so type
+#$ ./manage.py graph_models -a > db.dot
+#$ dot db.dot -T png -odb.png
+GRAPH_MODELS = {
+  'all_applications': True,
+  'group_models': True,
+}

ippisite/requirements.txt

 Django
 django-bootstrap3
-bioservices
\ No newline at end of file
+bioservices
+django-extensions
+pygraphviz
+pydot
+pyparsing