Add a helper for primary buttons
- create a helper for create_button.
- apply it in needed views.
- remove js functionality (application.js:66).
Fixes #12979 - Create helper for "new" button
Previously the button classes were applied to new buttons using jQuery.
This commit creates a `new_link` helper that makes sure all new buttons
will receive the correct class and only display if authorized. Also a
little bit of cleanup.