Added 'pull: local'

[siredmar]

Uses an already present docker image without pulling or building it. This can be useful if one has an docker image that shall get used without building it (e.g .image that was made with docker commit) or pulling it (e.g. no docker registry is present).

Example usage:

image=runtime:
  image: ubuntu
  tags: ["latest"]
  pull: local
  annotations:
    description: "image"

job=run:
  use: runtime
  command: ls
  annotations:
    description: "run"

In the above example dobi will use the local instance of ubuntu:latest and does not care pulling or building it.

[claassistantio]

All committers have signed the CLA.

[dnephin]

Thank you!