DDSXML — Fix inconsistent rules for references between elements

The syntax in DDS-XML contains places where an object references another object (e.g., topic_ref, domain_ref, type_ref or base_name). This is done normally using an attribute with type elementNameReference defined in http://www.omg.org/spec/DDS-XML/20170301/dds-xml_domain_definitions_nonamespace.xsd

However, this rule is not applied consistently throughout the schema files in the specification. More specifically, the XSD associated with Building Block QoS use elementName for base_name, which is incorrect.

Therefore, the definition of elementNameReference must be moved to the QoS building block, which is a dependency of all building blocks defining references.

Change type of all references to elementNameReference

The proposed solution moves the definition of elementNameReference from dds-xml_domain_definitions_nonamespace.xsd to dds-xml_qos_definitions_nonamespace.xsd and changes the type of all base_name attributes from elementName to elementNameReference.