ZeroCloud  tutorial, part 1

Partially depends on https://github.com/zerovm/zpm/pull/184. If https://github.com/zerovm/zpm/pull/184 is not accepted, this needs to be revised.

This slightly changes the structure of our docs. Zebra docs are pushed down and more emphasis is put on ZeroCloud. 

Most of this patch includes complete setup instructions for installing and running ZeroCloud on DevStack and setting up command clients. The only "real" tutorial included is based on https://github.com/zerovm/zerocloud/blob/swift-2.0/doc/Requests.md#post-any-other-file. Some other follow on tutorials have been stubbed out with `TODO` to give an idea of what comes next.