Allows AmpList arguments to be optional.

New submission from faldridge <None>:

Because AmpList overrides Argument.__init__(), but does not include the "optional" parameter in its argument list, AmpLists, unlike all other Amp Arguments, could not be designated as optional.

The attached patch simply adds this functionality to AmpList via its __init__ method.

The patch contains additional docstring information in AmpList.__init__() and passing unit tests.

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Type     : enhancement
Component: core
Keywords : review
Priority : highest
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3891