Added schema for db.

README.md

 # hpc_utilisation
 
-Python program to check the utilisation of HPC jobs using the PBS schedular.
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+Python program to check the utilisation of HPC jobs using the PBS schedular.
+
+In the Python code the `users_db_name` is a small sqlite database that just contains user information.
+The schema is:
+
+    $ echo '.schema' | sqlite3 users_ldap_public.db
+    CREATE TABLE IF NOT EXISTS "users" ( 'id' INTEGER NOT NULL, 'uts_id' TEXT NOT NULL, 'uts_email' TEXT, 'name' TEXT, PRIMARY KEY('id'));
+
+