Add support for simple element return types in soap methods

[veewee]

A response / request can be linked to a 'simple' element type:

            <element name="IFC_AcknowledgeReceipt" type="anyType" />

In that case, code generation resulted in MixedResult<IFC_AcknowledgeReceipt> but should be MixedResult<mixed>.

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://schemas.xmlsoap.org/wsdl/"
             xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
             xmlns:tns="http://example.com/customerdetails"
             xmlns:xsd="http://www.w3.org/2001/XMLSchema"
             targetNamespace="http://example.com/customerdetails"
             name="CustomerDetailsService">

    <!-- Data Types -->
    <types>
        <schema xmlns="http://www.w3.org/2001/XMLSchema"
                targetNamespace="http://example.com/customerdetails">
            <element name="IFC_AcknowledgeReceipt" type="anyType" />
        </schema>
    </types>

    <!-- Message Definitions -->
    <message name="GetCustomerDetailsRequestMessage">
        <part name="parameters" element="tns:IFC_AcknowledgeReceipt" />
    </message>
    <message name="GetCustomerDetailsResponseMessage">
        <part name="parameters" element="tns:IFC_AcknowledgeReceipt" />
    </message>

    <!-- Port Type (Abstract Interface) -->
    <portType name="CustomerDetailsPortType">
        <operation name="GetCustomerDetails">
            <input message="tns:GetCustomerDetailsRequestMessage" />
            <output message="tns:GetCustomerDetailsResponseMessage" />
        </operation>
    </portType>

    <!-- Binding (Concrete Implementation) -->
    <binding name="CustomerDetailsBinding" type="tns:CustomerDetailsPortType">
        <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http" />
        <operation name="GetCustomerDetails">
            <soap:operation soapAction="http://example.com/GetCustomerDetails" />
            <input>
                <soap:body use="literal" />
            </input>
            <output>
                <soap:body use="literal" />
            </output>
        </operation>
    </binding>

    <!-- Service Definition -->
    <service name="CustomerDetailsService">
        <documentation>This service provides customer details based on customer ID.</documentation>
        <port name="CustomerDetailsPort" binding="tns:CustomerDetailsBinding">
            <soap:address location="http://example.com/customerdetails/service" />
        </port>
    </service>
</definitions>