New associations and models: schedule versioning

For the schedule versioning in the admin interface (having multiple possible shcedules) we need to change some models and associations. It has also been create a rake:move_events_attributes task to migrate the data.

User Interface addapted to make use of the introduced associations and models

db/migrate/20160704091928_create_schedules.rb

@@ -0,0 +1,9 @@
+class CreateSchedules < ActiveRecord::Migration
+  def change
+    create_table :schedules do |t|
+      t.belongs_to :program, index: true
+      t.timestamps null: false
+    end
+    add_column :programs, :selected_schedule, :integer # Selected schedule ID
+  end
+end