api-templates: separate out selectors into a list

public/api-builder/angular.io-package/templates/directive.template.html

@@ -4,11 +4,14 @@
 
 {% block additional %}
 .l-main-section
-  h2 Selector
+  h2 Selectors
   .l-sub-section
+    {% for selector in doc.directiveOptions.selector.split(',') %}
     h3.selector
-      code {$ doc.directiveOptions.selector $}
+      code {$ selector $}
+    {% endfor %}
 
+{% if doc.inputs.length %}
 .l-main-section
   h2 Inputs
   .l-sub-section
@@ -19,7 +22,9 @@
     :markdown
 {$ property.memberDoc.description | indentForMarkdown(2) | trimBlankLines $}
   {% endfor %}
+{% endif %}
 
+{% if doc.ouputs.length %}
 .l-main-section
   h2 Outputs
   .l-sub-section
@@ -29,5 +34,6 @@
       code {$ property.memberDoc.classDoc.name $}.{$ property.propertyName $}
     :markdown
 {$ event.memberDoc.description | indentForMarkdown(2) | trimBlankLines $}
-  {% endfor %}
+{% endfor %}
+{% endif %}
 {% endblock %}