VanillaDockerApps from hub images without id specified result in a non-unique container name #313

If you deploy a VanillaDockerApp but don't supply an id: tag then the resulting container takes the name of the image being deployed which is non-unique thereby preventing additional instance of that app yaml being deployed.

For example:

location: my-docker-cloud
services:
- type: docker:nginx:latest
  name: nginx
  openPorts:
  - 80

results in the container called nginx, adding an id: nginx results in a unique container name nginx_<entityid>.