Add dockerversion to factory-parameters
    
    Currently, imagefactory's docker plugin will default an older
    version of the metadata imager format that is not compatible with
    the latest versions of docker. This change tells the plugin to use
    the docker version "1.10.1" metadata format which is compatible with
    all currently available docker releases.
    
    Signed-off-by: Adam Miller <maxamillion@fedoraproject.org>