simple theme update

- npm package update
- apply #1226
- implement vim help dialog
- display cookies and search URL with preferences
- allow to enable / disable Open Access DOI rewrite
- add a clear text button on the left of the search button
- implement #1011 : the HTML title page is not set when using POST
- remove searx/static/themes/simple/img/loader.gif
- use full width when only there are only images as result