Support for project_id

[larstobi]

I would like support for instances within a project_id, by specifying it in transport.yaml.

cloudstack:
  api_key: 'api_key'
  secret_access_key: 'secret_key'
  host: '127.0.0.1'
  port: '8080'
  path: '/client/api'
  scheme: 'http'
  project: 'project_id'

[aukjan]

second that, I am working on adding it .. if it works, I'll add a pull request ;)