Detect linked complexTypes as ResultInterface as well

[veewee]

Fixes #546 (comment), #550

The ResultAssembler is not able to detect wether an element with linked complexType is being used as the result.
More info: #546

    ->addRule(
        new Rules\IsResultRule(
            $engine->getMetadata(),
            new Rules\MultiRule([
                new Rules\AssembleRule(new Assembler\ResultAssembler()),
            ])
        )
    )

Given

<xs:complexType name="versionResponse">
    <xs:sequence>
        <xs:element minOccurs="0" name="version" type="xs:string" />
    </xs:sequence>
</xs:complexType>
<xs:element name="esfVersionResponse" nillable="true" type="tns:versionResponse"/>

This assembler can now detect that both esfVersionResponse and versionResponse should be marked as ResultInterface.

[rauanmayemir]

This works. 💃