[ADC-Ext 1.0.8] TTH reference in XML schema for TIGR

This is a proposal to update the TIGR proposal with a reference to the necessary changes to the XML schema.

The following changes are done to the file list XML schema:

A new type is defined with an appropriate attribute:

<xs:simpleType name=“tthType”>
<xs:restriction base=“xs:string”>
<xs:pattern value="[A-Za-z2-7]{39}"></xs:pattern>
<xs:attribute name=“TTH” type=“tthType”></xs:attribute>

The attribute is then referenced in the File element:

<xs:attribute ref=“TTH” use=“required”></xs:attribute>

This is now pushed to ADC-Ext 1.0.8.