Add default PASSWORD_RESET_TIMEOUT_DAYS environment variable value

Author: marlonkeating

democracylab/settings.py

@@ -485,3 +485,5 @@ def read_connection_config(config):
 
 MALICIOUS_URL_PATTERNS = os.environ.get('MALICIOUS_URL_PATTERNS', None)
 MALICIOUS_FWD_PATTERNS = os.environ.get('MALICIOUS_FWD_PATTERNS', None)
+
+PASSWORD_RESET_TIMEOUT_DAYS = os.environ.get('PASSWORD_RESET_TIMEOUT_DAYS', 7)