ENH: Add python cli automating versioning of Slicer wiki documentation

See https://www.slicer.org/wiki/Documentation/Nightly/Developers/ReleaseProcess#Update_Slicer_wiki

$ python wiki.py --help
usage: wiki.py [-h] [--log-level LOG_LEVEL] [--password PASSWORD]
               {query,copy,update} ...

This command-line tool allows to `version` Slicer mediawiki documentation. It
has three main modes of operation: ``query``, `copy` and ``update``.

positional arguments:
  {query,copy,update}   available sub-commands
    query               obtain version information
    copy                copy Nightly pages into RELEASE_VERSION namespace
    update              create and/or update wiki pages with RELEASE_VERSION

optional arguments:
  -h, --help            show this help message and exit
  --log-level LOG_LEVEL
                        Level of debug verbosity. DEBUG, INFO, WARNING, ERROR,
                        CRITICAL.
  --password PASSWORD   password for 'UpdateBot' user. By default, try to get
                        password from 'SLICER_WIKI_UPDATEBOT_PWD' environment
                        variable.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25571 3bd1e089-480b-0410-8dfb-8563597acbee