Consider "generic" cloud for cloud-init images
Per #159 (closed) -- cloud-init does have an auto-detect function which we could use to roll "generic" cloud images.
Tiny Cloud (at this time) does not have similar auto-detect functionality, or broad support for a large number of clouds.
Should also determine whether it's useful to continue having per-cloud cloud-init images, or if auto-detect is sufficient for the vast majority of use cases.