Fix Error on CalendarFolder.create_item, Add LegacyFreeBusyStatus Field to EWS.builder

Hello

I fixed following Error on CalendarFolder#create_item
NoMethodError: undefined method `[]' for #<Viewpoint::EWS::Template::CalendarItem subject="Test EWS", start=Fri, 24 Jan 2014 16:00:00 +0000, end=Fri, 24 Jan 2014 16:05:00 +0000, saved_item_folder_id={:id=>"AAMkADg1YjI0M2VlLTU2MzYtNDExYi05ZmVkLTc3OTgzNDFlYWNiNgAuAAAAAACzTAvmNJGNRrNf7gre/qkaAQDm1OaCknpjT5zXLqDAIeboAAAA2nYVAAA=", :change_key=>"AgAAABYAAAA1Kxwg4reMTKUPSng6zai3AABrtXO3"}>
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/bundler/gems/Viewpoint-e77191d7cb12/lib/ews/templates/calendar_item.rb:53:in `block in to_ews_item'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/bundler/gems/Viewpoint-e77191d7cb12/lib/ews/templates/calendar_item.rb:52:in `each'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/bundler/gems/Viewpoint-e77191d7cb12/lib/ews/templates/calendar_item.rb:52:in `to_ews_item'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/bundler/gems/Viewpoint-e77191d7cb12/lib/ews/templates/calendar_item.rb:42:in `to_ews_create'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/bundler/gems/Viewpoint-e77191d7cb12/lib/ews/types/calendar_folder.rb:41:in `create_item'
	from (irb):52
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
	from /Users/brandl/.rvm/gems/ruby-1.9.3-p194@sat_sor3.2/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'

This part of code is now the same like Viewpoint::EWS::Template::Task.

Furthermore I add the legacy_free_busy_state to EWS Builder. So it is possible to add this field on CalendarFolder#create_item