Adds saml as a config for authentication

[devanshu-m]

• Avalon has a requirement of adding providers as a config in the authentication file.
• We are also changing the provider strictly to saml

Changes:

• app/controllers/users/omniauth_callbacks_controller.rb: Change provider to saml
• app/views/devise/sessions/new.html.erb: show traditional login form only where database authentication is enabled, i.e., local development.
• config/initializers/omniauth.rb: change provider to saml
• config/routes.rb: add routes when not on local development machine
• config/settings.yml: turn off registrations
• lib/avalon/authentication.rb: add saml config to authentication if sp_key is present.