Reenable the note search API

Add a postgress freetext index on the note comments, and enable
note searching using freetext matching.

app/controllers/notes_controller.rb

@@ -255,16 +255,11 @@ class NotesController < ApplicationController
 
     # Get any conditions that need to be applied
     @notes = closed_condition(Note.all)
-    @notes = @notes.joins(:comments).where("note_comments.body ~ ?", params[:q])
+    @notes = @notes.joins(:comments).where("to_tsvector('english', note_comments.body) @@ plainto_tsquery('english', ?)", params[:q])
 
     # Find the notes we want to return
     @notes = @notes.order("updated_at DESC").limit(result_limit).preload(:comments)
 
-    # Disable notes search until we can make it scalable
-    response.headers['Error'] = "Searching of notes is currently unavailable"
-    render :text => "", :status => :service_unavailable
-    return false
-
     # Render the result
     respond_to do |format|
       format.rss { render :action => :index }