Add option to set projects "internal".

[Armin Fisslthaler]

[Sam Gleske]

https://github.com/gitlabhq/gitlabhq/blob/master/doc/api/projects.md#project-visibility-level

This would drop support for GitLab versions older than 6.4. The minimum GitLab version would be 6.4+.

public should be depracated in config.sh. A new config option should be provided.

• visibility - possible values: private, internal, public.

If public exists and not visibility then:

• public=true - means visibility is public.
• public=false - means visibility is private.

[Sam Gleske]

With older APIs of GitLab no longer being supported it makes sense to move forward with the visibility option.

[Chris Denneen]

@samrocketman I've put a stop gap in for now with #119
The removal of public completely as boolean in favor of visibility as a string would take a bit more work but guessing could be done with adding something similar to:

    parser.add_option("--public",dest="public",action="store_true",default=False)

    parser.add_option('--visibility,
                      type='choice',
                      action='store',
                      dest='visibility',
                      choices=['private', 'internal', 'public',],
                      default='private',)