Improve packetary documentation

[Sergey Yudin]

1) https://github.com/openstack/packetary/tree/master/doc/ there is only lorem ipsum, nothing really usefull. My suggestion is to maintain documentation in project rather than keeping it in internal Mirantis wiki.
 - add some verified yaml examples
 - installation, usage, etc. Basically verify and move content of https://mirantis.jira.com/wiki/display/PRD/Packetary onto project

2) arg-parser helpers is broken(or not even exist)
packetary --help returns
Commands:
Could not load EntryPoint.parse('build = packetary.cli.commands.build:BuildPackageCommand')
Could not load EntryPoint.parse('clone = packetary.cli.commands.clone:CloneCommand')
  complete print bash completion command
Could not load EntryPoint.parse('create = packetary.cli.commands.create:CreateCommand')
  help print detailed help for another command
Could not load EntryPoint.parse('packages = packetary.cli.commands.packages:ListOfPackages')
Could not load EntryPoint.parse('unresolved = packetary.cli.commands.unresolved:ListOfUnresolved')

[Ivan (ibogomazov)]

(.venv)arno@arno-wbook:~/packetary$ packetary --help
usage: packetary [--version] [-v | -q] [--log-file LOG_FILE] [-h] [--debug]
                 [--ignore-errors-num NUMBER] [--retries-num NUMBER]
                 [--retry-interval SECONDS] [--threads-num NUMBER]
                 [--http-proxy http://username:password@proxy_host:proxy_port]
                 [--https-proxy https://username:password@proxy_host:proxy_port]
                 [--cache-dir PATH]

The utility manages packages and repositories.

optional arguments:
  --version show program's version number and exit
  -v, --verbose Increase verbosity of output. Can be repeated.
  -q, --quiet Suppress output except warnings and errors.
  --log-file LOG_FILE Specify a file to log output. Disabled by default.
  -h, --help Show help message and exit.
  --debug Show tracebacks on errors.
  --ignore-errors-num NUMBER
                        The number of errors that can be ignored.
  --retries-num NUMBER The number of retries.
  --retry-interval SECONDS
                        The minimal time between retries in seconds.
  --threads-num NUMBER The number of threads.
  --http-proxy http://username:password@proxy_host:proxy_port
                        The URL of http proxy.
  --https-proxy https://username:password@proxy_host:proxy_port
                        The URL of https proxy.
  --cache-dir PATH The path to the directory which be used for cache.

Commands:
  build Builds the new package.
  clone Clones the specified repository to local folder.
  complete print bash completion command
  create Creates the new repository.
  help print detailed help for another command
  packages Gets the list of packages from repository(es).
  unresolved Gets the list of external dependencies for repository(es).

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/345447
Committed: https://git.openstack.org/cgit/openstack/packetary/commit/?id=c46465c3255a9f5e59a05b8701e06054df39f32f
Submitter: Jenkins
Branch: master

commit c46465c3255a9f5e59a05b8701e06054df39f32f
Author: Ivan Bogomazov <email address hidden>
Date: Thu Jul 21 16:58:42 2016 +0300

    Add documentation for packetary

    Closes-bug: #1604989
    Closes-bug: #1604996

    Change-Id: Ib214006c4852af9b08702368d55f157f7bba089a