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

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

docs/dgeni-package/templates/lib/paramList.html

@@ -0,0 +1,7 @@
+{% macro paramList(params) -%}
+  {%- if params -%}<span class="params">(
+    {%- for param in params -%}
+      <span class="param">{$ param $}{% if not loop.last %}, {% endif %}</span>
+    {%- endfor %})</span>
+  {%- endif %}
+{%- endmacro -%}