Annotate terms with the party who is the obliged party of a particular term

Often it is necessary to also represent obligations of a service customer to an agreement, e.g., to provide a stage-in 
file on time. For this purpose, it is necessary to be able to annotate terms, in particular guarantee terms, with the 
obliged party. 

Proposed change of the schema:

	<xs:complexType name="TermType" abstract="true">
		<xs:attribute name="Name" type="xs:NCName" use="optional"/>
		<xs:attribute name="Obliged" type="xs:NCName" use="optional"/>
	</xs:complexType>

The default Obliged should be the service provider.