chore(doc-gen): add createDecoratorDocs processor

The createDecoratorDocs processor identifies docs of exports that actually
represent decorators and get useful information for them.

This commit also set up the rest of the generation to display these new
decorator docs with their own template and updates the API list so that
we can filter the docs by decorator docType.

tools/api-builder/angular.io-package/index.js

@@ -92,6 +92,13 @@ module.exports = new Package('angular.io', [basePackage, targetPackage, cheatshe
     outputPathTemplate:'${moduleDoc.moduleFolder}/${name}-${docType}.jade',
   });
 
+
+  computePathsProcessor.pathTemplates.push({
+    docTypes: ['decorator'],
+    pathTemplate: '${moduleDoc.moduleFolder}/${name}-${docType}.html',
+    outputPathTemplate:'${moduleDoc.moduleFolder}/${name}-${docType}.jade',
+  });
+
   computePathsProcessor.pathTemplates.push({
     docTypes: ['jade-data'],
     pathTemplate: '${originalDoc.moduleFolder}/_data',

tools/api-builder/angular.io-package/templates/decorator.template.html

@@ -0,0 +1,23 @@
+{% include "lib/githubLinks.html" -%}
+{% include "lib/paramList.html" -%}
+{% extends 'layout/base.template.html' %}
+
+{% block body %}
+include {$ relativePath(doc.path, '_util-fns') $}
+.l-main-section
+  h2(class="decorator export")
+    pre.prettyprint
+      code.
+        export {$ doc.name $}(options : {@link {$ doc.decoratorType $} {$ doc.decoratorType | escape $}}){$ returnType(doc.returnType) $}
+
+  p.location-badge.
+    exported from {@link {$ doc.moduleDoc.id $} {$doc.moduleDoc.id $} }
+    defined in {$ githubViewLink(doc) $}
+
+  :marked
+{%- if doc.notYetDocumented %}
+    *Not Yet Documented*
+{% else %}
+{$ doc.description | indentForMarkdown(4) | trimBlankLines $}
+{% endif -%}
+{% endblock %}