Describe image customizations to support resize.

Add a section to describe how images should be customized to support
OpenStack.

In particular, it adds a section that describes how to support
resizing partitions on boot.

Patchset has minor edits (wilil for will).

Change-Id: I890f6cce5eeb11852f3e9dbb87e16afba1862d1a
Fixes a couple of cross reference problems; scales arch images.

Change-Id: I6e01842c87743696043f58160b0cab9ca0b28912
Merge "Describe image customizations to support resize."