Added cassandra as dependency for contrail

This need parameter seeds which is an array of IP of all
cassandra servers - this is only required in case of mult-node
setup.

Note: service discovery may not be able to handle this scenario as this have
multi-node cross dependency (in initial phase).
Merge pull request #62 from hkumarmk/contrail_cassandra

Added cassandra as dependency for contrail
Commit vbox specific vagrant environment

This commits adds a specific deployment environment
based on vagrant with the virtualbox provider.

It also removes the dan environment which was previously
defining the same environment.
Add data overrides for acceptance test deployments

Add cross data lookups to support openstack deployments.
Add contrail role
Update role specifications

To use the currently functional openstack roles.
Add contrail role to vagrant