when updating, create data dump first

closes #58

Utils/update.sh

@@ -15,6 +15,10 @@ if [ "$1" = "--prod" ]; then
     export DJANGO_SETTINGS_MODULE=AKPlanning.settings_production
 fi
 
+# before potentially breaking anything, create a data backup
+mkdir -p backups/
+python manage.py dumpdata --indent=2 > "backups/$(date +"%Y%m%d%H%M")_datadump.json" --traceback
+
 git pull
 pip install --upgrade setuptools pip wheel
 pip install --upgrade -r requirements.txt