EZP-21527: Simple search with platform stack

Link: https://jira.ez.no/browse/EZP-21527

## Description
Implements the search using the platform stack.

## TODO
- [x] Handle request caching
- [x] Modify the search form in the header of the page to call the new stack search. Done by @crevillo 
- [x] Add GET param from the form in the pager fanta urls (previous, next, etc)
- [x] Remove debug values from config files
- [x] Rebase commits

yes they are already cached, using esi so will not be cached as part of this.

However you have a very valid point, if some content is deleted there will be a window of the length of the ttl where it might throw exception on missing content.
So maybe we need to remove this and recommend people to use Solr/ElasticSearch which we hope to ship in 5.4 as well.