Rename docker directory to heat_docker

This directory was renamed in 4e8231, which made importing docker
(that is docker-py) difficult if not impossible in Python 2.x. So
rename it to something other than 'docker' to avoid that problem.

(setup.cfg has been modified with the new path)

Change-Id: I3cbb7c5d4b53f70e1dc6102881f8e05852341a9a
Related-bug: #1296758
get docker driver from master

Change-Id: I281e626707463ecddc20d11d8305c1e7e16bf8fe
remove containers on delete

This patch calls client.remove_container after a container has stopped
running in response to client.kill.

In the event that a container is created with an explict name, as in:

  docker_dbserver:
    type: "DockerInc::Docker::Container"
    properties:
      image: mysql
      name: dbserver

Failure to remove the container on delete will prevent the stack from being
re-deployed.

Change-Id: Ic864d1a808b303fcb58815b87e55a0e7d1639bbb
closes-bug: #1364019
patch for icehouse compatability

Change-Id: I102b5000df2040bfc2025261db1363a6ecdc2b45