Add documentation listing the openSUSE images and their differences

As tracked in Trello [1]. List of published Crowbar openSUSE builds and
their intended usage.

[1] https://trello.com/card/document-differences-between-opensuse-appliances/50809fb54fa7ad9c1a000f4d/148
Merge pull request #1776 from jamestyj/jamestyj-opensuse-appliances

Add documentation listing the openSUSE images and their differences