Reenable the note search API

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

db/migrate/20140115192822_add_text_index_to_note_comments.rb

@@ -0,0 +1,11 @@
+require 'migrate'
+
+class AddTextIndexToNoteComments < ActiveRecord::Migration
+  def up
+    add_index :note_comments, [], :columns => "to_tsvector('english', body)", :method => "GIN", :name => "index_note_comments_on_body"
+  end
+
+  def down
+    remove_index :note_comments, :name => "index_note_comments_on_body"
+  end
+end