- Fixed typo in function name
Added support for docker image types

kiwi supports creation of lxc images which are stored below
var/lib/lxc/<container-name>. The docker subsystem expects
the image to be packed differently. Thus we added a new type:

    <type image="docker">

The information about the container name is optional in this
case and if specified not used for docker type images
- Fixed container image name extension
  * if docker is set the extension should be set to docker and not lxc
Merge pull request #347 from openSUSE/review_140430_docker

[Review] Request from 'schaefi' @ 'openSUSE/kiwi/review_140430_docker'