ParserOutput object.
&$output: ParserOutput, to manipulate or replace
+'ContentAlterParserOutput': Modify parser output for a given content object.
+Called by Content::getParserOutput after parsing has finished. Can be used
+for changes that depend on the result of the parsing but have to be done
+before LinksUpdate is called (such as adding tracking categories based on
+the rendered HTML).
+$content: The Content to render
+$title: Title of the page, as context
+$parserOutput: ParserOutput to manipulate
+
'ConvertContent': Called by AbstractContent::convert when a conversion to another
content model is requested.
$content: The Content object to be converted.