Extract template / csv utility code into modules

This follows a similar approach to the previous commits, noting that
one module depends on the other, so we have to extract both together.

app/main/views/tour.py

@@ -9,7 +9,7 @@ from app.main.views.send import (
     get_placeholder_form_instance,
     get_recipient_and_placeholders_from_session,
 )
-from app.utils import get_template
+from app.utils.templates import get_template
 from app.utils.user import user_has_permissions