Added upgrade process from Essex to Folsom.

It covers Keystone, Glance, Nova and nova-volume to Cinder upgrade,
but lacks nova-network to Quantum.

Patchset does minor style and spelling fixes.

Making sure that the style fixes get in too by testing the merge.
Sorry about the lack of "git add" on my part with the file rename.

bug #1043032
DocImpact

Change-Id: I57b351a83ab00eb13871e7780e320c09e31482d9
Merge "Added upgrade process from Essex to Folsom."