preview for page, post and program

...trollers/admin/communication/websites/pages_controller.rb

...trollers/admin/communication/websites/posts_controller.rb

app/controllers/admin/education/programs_controller.rb

...views/admin/communication/websites/posts/preview.html.erb

app/views/admin/communication/websites/posts/show.html.erb

app/views/admin/education/programs/preview.html.erb

app/views/admin/education/programs/show.html.erb

app/views/admin/layouts/preview.html.erb

config/routes/admin/communication.rb

config/routes/admin/education.rb