Description
All MS Office document custom properties should be parsed and returned in the Metadata set. This would be consistent with how all HTML meta tags are parsed and returned.
CustomProperties are already being parsed to produce the Metadata.LANGUAGE property when normalizing document properties into the Dublin Core metadata set. With minor modifications to the org.apache.tika.parser.microsoft.SummaryExtractor class the entire set of Custom Properties could be obtained and set for the document metadata.