chore(doc-gen): convert private classes to interfaces in the docs

Closes #3576

docs/docs-package/index.js

@@ -15,6 +15,7 @@ module.exports = new Package('angular-v2-docs', [jsdocPackage, nunjucksPackage,
 .factory(require('./readers/ngdoc'))
 
 // Register the processors
+.processor(require('./processors/convertPrivateClassesToInterfaces'))
 .processor(require('./processors/generateNavigationDoc'))
 .processor(require('./processors/extractTitleFromGuides'))
 .processor(require('./processors/createOverviewDump'))

docs/docs-package/processors/convertPrivateClassesToInterfaces.js

@@ -0,0 +1,10 @@
+module.exports = function convertPrivateClassesToInterfacesProcessor(convertPrivateClassesToInterfaces) {
+  return {
+    $runAfter: ['processing-docs'],
+    $runBefore: ['docs-processed'],
+    $process: function(docs) {
+      convertPrivateClassesToInterfaces(docs, false);
+      return docs;
+    }
+  };
+};