chore(doc-gen): add method signatures to members and functions

Closes https://github.com/angular/dgeni/issues/124

docs/dgeni-package/templates/function.template.html

@@ -0,0 +1,9 @@
+{% include "lib/paramList.html" -%}
+{% extends 'layout/base.template.html' -%}
+
+{% block body %}
+<h1 class="function export">{$ doc.name $}{$ paramList(doc.parameters) $}</h1>
+<p class="module">exported from <a href="/{$ doc.moduleDoc.path $}">{$ doc.moduleDoc.id $}</a></p>
+<p>{$ doc.description | marked $}</p>
+
+{% endblock %}