Add a way to start up an app with new empty volumes.

[wallnerryan]

If I have no existing snapshots or volumesets, i would like to bootstrap a compose app with empty fli volumes.

example

fli-docker -f fli-manifest -new

Where the manifest may look like

docker_app: cassandra.yml

flocker_hub:
    endpoint: https://data.flockerhub.clusterhq.com

volumes:
    - name: cassandra1
      snapshot:
      volumeset: cassandra-snapshots-01
    - name: cassandra2
      snapshot:
      volumeset: cassandra-snapshots-01
    - name: cassandra3
      snapshot:
      volumeset: cassandra-snapshots-01

Such that, empty volumes would be created in volumeset cassandra-snapshots-01 and if volumeset doesnt exist maybe use a -create-vs flag or something and the volumeset will get created locally first.