Add an option to start command so a CA can be passed to allow communication with iRODS servers

[jmtcsngr]

When using TLS to communicate with an iRODS server it is possible the iRODS service is running with a certificate which is not signed by certificate authority (CA) chain provided in the default system paths. It would be useful to be able to pass a path to a file with a CA chain. go-irodsclient seems to support both: using system CA as default or using a CA if provided. The CA passed should be use exclusively for sqyrrl <-> iRODS communication.