Possibility to turn off or customize version/help option

**Issue by [ptylenda](https://github.com/ptylenda)**
_Monday Sep 19, 2016 at 14:43 GMT_
_Originally opened as https://github.com/gsscoder/commandline/issues/351_

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It would be a good idea to make it possible to turn off (or at least customize) version and help options, probably via an attribute for the options class. This especially concerns version option - we are migrating from old custom parsers to the CommandLine library and we have noticed that it conflicts with our custom version option (-v, --version). This option is unrelated to version of an application, it concerns version of a file being processed by the executable. In our case it is not possible to use a different option name as we have to maintain 100% backward compatibility inside an enterprise system. Fortunately this "conflict" seems to be only visible in the help screen, when both our custom option and the default option are displayed at once.