add basic support for labels

db/migrate/20141120202853_add_labels.rb

@@ -0,0 +1,15 @@
+class AddLabels < ActiveRecord::Migration
+  def change
+    create_table :labels do |t|
+      t.string :name
+      t.references :role
+    end
+
+    add_column :forumthreads, :label_id, :integer
+
+    create_table :forums_labels, id: false do |t|
+      t.references :forum
+      t.references :label
+    end
+  end
+end