Delete unused Jinja macros and rearrange templates.

Templates and fragments that relate to specific resources (portfolios,
applications, task orders) should reside in directories named for the
relevant resource. This also matches the way the application routes are
distributed among modules named for each resource type.

templates/task_orders/step_4.html

@@ -13,5 +13,5 @@
 {% endblock %}
 
 {% block to_builder_form_field %}
-    {% include "fragments/task_order_review.html" %}
+    {% include "task_orders/fragments/task_order_review.html" %}
 {% endblock %}