Updated container create method parameters and Config definition

Hi Andrea,

In this PR I have fixed four issues I found during a quick test I did with this docker jclouds API:

1. As I found container create API method [1] accept image name in "image" parameter, however it was set to image id. I have changed this to image name.
2. The command parameters ("/usr/sbin/sshd", "-D") passed in container create API method caused the container to stop soon after it was started. May be this should be configurable to the client. WDYT?
3. I had to set attachStdout and attachStderr properties to true in container create API method to avoid the same problem as in point 2.
4. The entrypoint property in Config class has been changed to a List<String> in docker remote API v1.11. I have updated it accordingly.

[1] http://docs.docker.io/reference/api/docker_remote_api_v1.11/

Thanks