Parameter Description Should Default to Parameter Descriptor Documentation

[commonsensesoftware]

An operation parameter.description never contains a default description even though one might be provided by ApiParameterDescription.Documenation might provide one. In most cases, the description will come from XML comments, but not necessarily always.

The description should use the default value provided as so in the SwaggerGenerator.cs:

parameter.description = paramDesc.Documentation;

Although not 100% required, it is probably worth updating ApplyXmlActionComments.cs so that the description is only updated when there is a parameter XML node with a non-empty value.