Remove tokenfield typeahead

[jorg-vr]

This pull request removes tokenfield/typeahead.

All uses had already been removed by #4023, #4083 and #3498

I also removed all mentions of the vendor folder, as this was the last module using that system.

I moved the css we still use for tokens to components/tokens.css.scss in order to get rid of mentions of the old tokenfield component.

Part of #3590

[chvp]

For the DB changes: it's probably the easiest to do a db reset; this should re-initialize your db using the schema.rb.