The command by which the PostgreSQL interactive terminal 'psql' is
called.

If the PostgreSQL binaries are in your system's PATH, the command can
be as simple as 'psql' (on UNIX) or 'psql.exe' (on Windows).

It may be necessary to provide the full filename. Use the 'Paste
filename' button browse and paste the full filename.

Examples:

    - UNIX: /usr/bin/psql
            /opt/postgresql/bin/psql

    - Windows:
           C:/Program Files/PostgreSQL/r8.0.0-rc2/bin/psql.exe

           Note: Use '/' instead of '\' as directory name separator.

