ajoute une commande make wipe (#4211)

Makefile

@@ -83,6 +83,11 @@ watch-front:
 
 clean: clean-back clean-front
 
+wipe:
+	rm base.db
+	rm -rf contents-private/*
+	rm -rf contents-public/*
+
 doc:
 	cd doc && \
 	make html
@@ -111,6 +116,7 @@ help:
 	@echo "  clean-back        to clean *.pyc"
 	@echo "  clean-front       to clean frontend builds"
 	@echo "  clean             to clean everything"
+	@echo "  wipe              to clean data (database and contents)"
 	@echo "  watch-front       to watch frontend code"
 	@echo "  migrate           to migrate the project"
 	@echo "  report-release-back  to generate release report"