Add button to show and hide password in the devise registrations form

Makes it easy for a user to check that he have typed the password correctly.

app/assets/javascripts/application.js

@@ -39,6 +39,7 @@
 //= require osem-bootstrap
 //= require osem-revisionhistory
 //= require osem-commercials
+//= require osem-register
 //= require unobtrusive_flash
 //= require unobtrusive_flash_bootstrap
 //= require countable