unify token as top level element & as reference, both allow name

Author: Weiwu Zhang

schema/tokenscript.xsd

@@ -51,6 +51,7 @@
                 <element minOccurs="0" maxOccurs="unbounded" ref="dsig:Signature"/>
             </sequence>
             <attribute name="custodian" type="boolean" default="false"/>
+            <attribute name="name" type="NCName"/>
         </complexType>
         <keyref name="typeRef" refer="ts:namedTypeName">
             <selector xpath=".//ts:origins/ethereum:event|.//ts:origins/ethereum:call"></selector>