Add support for NiFi Registry properties files to TLS-toolkit in nifi-toolkit

Currently, when running the TLS-toolkit in standalone mode there is an option to specify a nifi.properties file to update, where the updated version containing the keystore and truststore files will be written in the output directory for each hostname.

Because the admin guide for NiFi Registry will include instructions for how to use the NiFi toolkit for generating keys/certs, it would be nice that if a user passes a NiFi Registry properties file path to the --nifiPropertiesFile argument, the TLS tool will gracefully understand that and output an updated NiFiRegistry properties file.