Modified README.txt.

You can access the file catalog from the 'client' container:

    1) Access the db via psql client (password: postgres):

    $ psql -h file_catalog -U postgres -d vospace_testdb

    2) You can now perform a query, for example show all the tuples of the Node table:

    vospace_testdb=# SELECT * FROM Node;

    2) You can now perform a query, for example show all the tuples of the Node table displaying some fields:

    vospace_testdb=# SELECT node_id, parent_path, path, name, type, owner_id, creator_id, content_MD5 FROM Node;

 The default output of the query after the container initialization should be something like this:

  node_id | parent_path | path |  name  |   type    | owner_id | creator_id | content_md5 

 ---------+-------------+------+--------+-----------+----------+------------+--------------

        1 |             |      |        | container | 3354     | 3354       |             

        2 |             | 2    | home   | container | 3354     | 3354       |             

        3 | 2           | 2.3  | curban | container | 3354     | 3354       |             

 (3 rows)

 Now, open a shell on the 'transfer_service' container and launch 'store_preprocessor.py', with:

 $ docker exec -it transfer_service /bin/bash

 $ python3 store_preprocessor.py 

 The new output of the query will be the following, because a new file called 'foo.txt' was placed in /home/curban/store:

  node_id | parent_path |   path    |        name         |   type    | owner_id | creator_id |           content_md5            

 ---------+-------------+-----------+---------------------+-----------+----------+------------+----------------------------------

        1 |             |           |                     | container | 3354     | 3354       | 

        2 |             | 2         | home                | container | 3354     | 3354       | 

        3 | 2           | 2.3       | curban              | container | 3354     | 3354       | 

        4 | 2.3         | 2.3.4     | store               | container | 3354     | 3354       | 

        5 | 2.3.4       | 2.3.4.5   | 2020_12_02-11_31_56 | container | 3354     | 3354       | 

        6 | 2.3.4.5     | 2.3.4.5.6 | foo.txt             | data      | 3354     | 3354       | d41d8cd98f00b204e9800998ecf8427e

 (6 rows)

 To stop the whole environment:

 $ docker-compose down