Attribute and method for specifying the behavior of repeated uses of collection options

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When an option for collection options is passed to the parser multiple times, 
the default behavior is to append all values to the collection.

Add an attribute and method for autowired and stand alone options which lets 
the user of the parser specify a behavior for repeated use.

  * CollectionRepeatBehavior.Clear
  * CollectionRepeatBehavior.Append (default, append values from repeated uses to collection)
  * CollectionRepeatBehavior.Error

Clear means that collection values should be cleared and only the values of the 
last use should be kept. When used with stand alone options, the handler should 
only be called for the values of the first use.

Original issue reported on code.google.com by michael.praschl on 21 Mar 2013 at 7:29