Update front end for the new authentication system

Add simple_form.
Update several forms to bootstrap and simple_form.
Add Log in, Log out, Register, and Profile links to the navigation bar.
Add a collection selection to the Status form.
Add if_user_signed_in? test to display appropriate links.
Add protected variables to application_controller.
Add private set_status and status_params to statuses_controller.
Add def full_name to models\user.rb.