Allow to override voters_upload from environment

settings.py

@@ -189,7 +189,7 @@ HELP_EMAIL_ADDRESS = get_from_env('HELP_EMAIL_ADDRESS', 'help@heliosvoting.org')
 AUTH_TEMPLATE_BASE = "server_ui/templates/base.html"
 HELIOS_TEMPLATE_BASE = "server_ui/templates/base.html"
 HELIOS_ADMIN_ONLY = False
-HELIOS_VOTERS_UPLOAD = True
+HELIOS_VOTERS_UPLOAD = (get_from_env('HELIOS_VOTERS_UPLOAD', 1) == 1)
 HELIOS_VOTERS_EMAIL = True
 
 # are elections private by default?