Making the plugin active. It's rudimentary, but works when I pass in the PDFBox command as the cmdline conversion cmd. Other types of commands not tested. Correction to previous commit message: An earlier commit succeeded in putting the extracted text into doc.xml, but no text was visible in when previewing the extracted HTML version of the doc. Kathy pointed out that the NoText meta had been set to 1. 'This doc has no text' was also appended to the doc.xml's Content node. Overrode add_dummy_text to do nothing, so that when superclass UnknownPlugin::process called it, the NoText and dummytext wouldn't be set. This fixed the problem on preview.