Correct the port group defined location in vmware guide

The right port group defined location is section [DEFAULT]
"neutron_ovs_bridge=" in file nova.conf, if using vcenter
driver with OpenStack Networking Service and OVS agent.

Change-Id: I9430afa843cc44694b7aca11793ec0fb640b49c6
(cherry picked from commit 40ec040797b98444d6a1d7eb0bd614f7bd9338c2)
Install guide: recommend 64-bit OS

Add some text to the install guide to recommend installing a 64-bit
operating system. Also links to Ops Guide for system requirements.

Motivated by this comment in the docs:
http://docs.openstack.org/havana/install-guide/install/apt/content/nova-boot.html#comment-1146233396

Change-Id: Iabe612024be0f6fcf335cf2daaf3ea77bed3cd86
backport: havana
(cherry picked from commit 57ddfbf2246d7b7e8b551e9d10049d17794a8eb9)
Merge "Install guide: recommend 64-bit OS" into stable/havana
Merge "Correct the port group defined location in vmware guide" into stable/havana