Document how to make a HIL server handle more requests

[henn]

There are certain things one can do to handle more requests that we should document. We've hit these while running various benchmarks that are trying to do things in parallel. These include:

• Increasing the processes attribute in WSGIDaemonProcess to something like 128
• Maybe increasing the number of apache listeners to accommodate the extra WSGI Daemons.
• Increasing postgres's max connection count by modifying max_connections in /var/lib/pgsql/data/postgresql.conf

[xuhang57]

@naved001 do we have any documentation about multi-process at all so far?