Added support for STI deliverables

* HourlyDeliverables cost are based on the time used
* FixedDeliverables are based on a flat rate
* Added a checkbox on the new Deliverable form to pick which one to use

  #1135

app/views/deliverables/_form.html.erb

@@ -17,8 +17,10 @@
       </div>
 
       <div class="splitcontentright">
-        <%# TODO: Need to update subtotals with observers %>
-        <p>TODO: Fixed cost</p>
+        <p>
+          <label for="deliverable_type">Fixed Cost</label>
+          <%= check_box(:deliverable, :type, {}, FixedDeliverable.name, HourlyDeliverable.name) %>
+        </p>
 
         <p><%= f.text_field :cost_per_hour, :size => 7 %></p>
         <%= observe_field('deliverable_cost_per_hour', :function => "new Budget.updateAmounts();") %>