build(aio): refactor dgeni packages

This is to tidy up the `author-packagse`, which currently duplicates a
lot of the configuration in the main packages. We need to
DRY this up so that we don't fall foul of a change in one being missed in
the other.

aio/tools/transforms/angular-base-package/processors/createOverviewDump.js

@@ -0,0 +1,24 @@
+var _ = require('lodash');
+
+module.exports = function createOverviewDump() {
+
+  return {
+    $runAfter: ['processing-docs'],
+    $runBefore: ['docs-processed'],
+    $process: function(docs) {
+      var overviewDoc = {
+        id: 'overview-dump',
+        aliases: ['overview-dump'],
+        path: 'overview-dump',
+        outputPath: 'overview-dump.html',
+        modules: []
+      };
+      _.forEach(docs, function(doc) {
+        if (doc.docType === 'module') {
+          overviewDoc.modules.push(doc);
+        }
+      });
+      docs.push(overviewDoc);
+    }
+  };
+};