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

app/models/schedule.rb

@@ -0,0 +1,4 @@
+class Schedule < ActiveRecord::Base
+  belongs_to :program
+  has_many :event_schedules, dependent: :destroy
+end