Add API for burndown chart

Refs #4220

Used by the dev dashboard.

app/controllers/rb_burndown_charts_controller.rb

@@ -5,9 +5,23 @@ class RbBurndownChartsController < RbApplicationController
 
   def show
     @burndown = @sprint.burndown
-
+    @dash = {
+      :data => [ {:label => "committed",
+                  :data => @burndown.points_committed.each_with_index.map{ |p, i| [i + 1, p] }},
+                 {:label => "remaining",
+                  :data => @burndown.points_to_resolve.each_with_index.map{ |p, i| [i + 1, p] }},
+                 {:label => "ideal",
+                  :data => @burndown.ideal.each_with_index.map{ |p, i| [i + 1, p] }} ],
+      :options => { :xaxis => {:ticks => @burndown.days.each_with_index.map{ |d, i| [i + 1, d.strftime("%a")] },
+                               :show => true,
+                               :min => 1,
+                               :max => @burndown.days.size},
+                    :yaxis => { :min => 0 },
+                    :legend => {:position => "sw"} } }
+
     respond_to do |format|
       format.html { render :layout => false }
+      format.json { render :json => @dash.to_json }
     end
   end