Add break to ordergroup

In some foodcoops it is possible that ordergroups make a break. During that
they e.g. pay reduced or no membership fees and do not need to do work for
the foodcoop. This new fields make this visible to all members.

db/migrate/20160217164552_add_break_to_group.rb

@@ -0,0 +1,6 @@
+class AddBreakToGroup < ActiveRecord::Migration
+  def change
+    add_column :groups, :break_start, :date
+    add_column :groups, :break_end, :date
+  end
+end

db/schema.rb

@@ -141,6 +141,8 @@ ActiveRecord::Schema.define(version: 20160217194036) do
     t.integer  "next_weekly_tasks_number", limit: 4,                              default: 8
     t.boolean  "ignore_apple_restriction",                                        default: false
     t.boolean  "role_invoices",                                                   default: false, null: false
+    t.date     "break_start"
+    t.date     "break_end"
   end
 
   add_index "groups", ["name"], name: "index_groups_on_name", unique: true, using: :btree