Change build_database script to login directly to ICAT rather than via the SEPIA backend API
Change the build_database.py script to use the module icat.config from python-icat.  This enables the following features provided by that module:
- configuration via config file and additional command line options,
 - no need to get the name of the ICAT authenticator plugin and credentials from the environment,
 - login directly to ICAT, bypassing the SEPIA backend API.
 
This will also be needed, because we will disallow login to admin accounts at the SEPIA backend API.