code: private String parseQName() {
  
          String qName = parseNCName(); // can be prefix or localPartName
  
          if (is(TokenType.COLON, false)) {
  
              qName += ":";
              qName += parseNCName(); // is localPartName
          }
  
          return qName;
      }
docs: Parses the the rule QName according to the following production rule:
  http://www.w3.org/TR/REC-xml-names
  <p>
  [7] QName ::= PrefixedName | UnprefixedName
  </p>
  <p>
  [8] PrefixedName ::= Prefix ':' LocalPart
  </p>
  <p>
  [9] UnprefixedName ::= LocalPart
  </p>
  <p>
  [10] Prefix ::= NCName
  </p>
  <p>
  [11] LocalPart ::= NCName => QName ::= (NCName ":" )? NCName .
  </p>
  
  @return string representation of QName