Holding state for installation root dir in ESGF_INSTALL_PREFIX
Still preserve the use of 'install_prefix' var name
Establish ESGF_INSTALL_WORKDIR and environment equiv to 'workdir' - where installed artifacts are downloaded and built before they get installed under ESGF_INSTALL_PREFIX
Instructing on use of environment vars to customize install locations...

deprecated the use of --prefix and --workdir
Extended usage message to instruct about environment vars

        --------------
        Key Environment Vars:
        --------------

        The following variables are written to the /etc/esg.env file
        which sets up the installation environment.  The 'OFFICIAL'
        names (not the [common_names]) should be used in that file.

        (Nomenclature: OFFICIAL_ENV_VARIABLE_NAME [common_name] : either can be set; common name overrules)

        ESGF_HOME [esg_root_dir]
                    The location where configuration files are kept (the node's state)
                    (default - /esg)
        ESGF_INSTALL_PREFIX [install_prefix]
                    Top level directory where core node artifacts are installed
                    (default - /usr/local)
        ESGF_USER_HOME [installer_home]
                    Directory where the installation user's home directory is.
                    Here for historical reasons when this user's home was used to download and build artifacts.
                    It prefixes the ESGF_INSTALL_DIR [workdir] if it is not explicitly set
                    (default - /usr/local/src/esgf)
        ESGF_INSTALL_WORKDIR [workdir]
                    Top level directory where core node artifacts are downloaded and built
                    (default - /workbench/esg)

        --------------
        Typical usage:
        --------------

        Installation : esg-node --install --verify
            (submit csr and get back returned cert)
        Credentials  : esg-node --install-ssl-keypair <pub_cert> <priv_key>
        Test Publish : esg-node --test-pub
        Update Certs : esg-node [--force] --rebuild-truststore
        Life Cycle   : esg-node [start|stop|status|restart|update]

         ___ ___  ___ ___
        | __/ __|/ __| __|
        | _|\__ \ (_ | _|
        |___|___/\___|_|

# esg-node --prefix foo

    DEPRECATED: The --prefix flag has been deprecated.
             Instead, please use the environment variable ESGF_INSTALL_PREFIX

    Ex: bash> ESGF_INSTALL_PREFIX=/usr/local /usr/local/bin/esg-node ...

# esg-node --workdir bar

    DEPRECATED: The --workdir flag has been deprecated.
             Instead, please use the environment variable ESGF_INSTALL_WORKDIR

    Ex: bash> ESGF_INSTALL_WORKDIR=/usr/local/src/esgf/workbench/esg /usr/local/bin/esg-node ...