Setup basic Revision History page

Sets up paper_trail tracking in important models

and add conference_id to versions for storing conference_id
of conference related objects  as metadata.This will help in querying
for versions related to conferences.

Fix issues with factories & event types initialization.Import paper_trail testing helpers
Fix bug: Creating an event creates a useless version with event update

Add revert and view changes features to revision history

app/models/venue.rb

@@ -4,6 +4,8 @@ class Venue < ActiveRecord::Base
   has_many :rooms, dependent: :destroy
   before_create :generate_guid
 
+  has_paper_trail ignore: [:updated_at, :guid], meta: { conference_id: :conference_id }
+
   accepts_nested_attributes_for :commercial, allow_destroy: true
   validates :name, :street, :city, :country, presence: true