NEW MODULE: docker_image module for building docker images + Docker > 0.7 support

##### Issue Type:

Feature Pull Request
New Module Pull Request

##### Ansible Version:

ansible 1.5

##### Environment:

OS X 10.9.1

##### Summary:

To docker module added 0.7 features: 
- host to container port binding
- container linking 

Adds new docker_image module to build, check and remove images from host image storage

##### Steps To Reproduce:

Start docker container, bind internal container port 800 to docker interface (172.17.42.1) and port 80, link with PostgreSQL container (path ports and volumes from one container to another): 

    - name: "Start new app container"
      docker:
        image: "my/app"
        name: "app1"
        links:
          - service_postgresql:db
        port_bindings:
          - 8000:172.17.42.1:80
        state: present
      tags:
        - deploy
        - start

For image building:
```
 - name: "Create image"
    docker_image: path="/path/to/build/dir" name="my/app" state="present"
```
For more examples see module docs

##### Expected Results:

N/A

##### Actual Results:
N/A