Claas Kazzer authored Jun 05, 2019 and Dorian Merz committed Jun 11, 2019

* reworks header as flex containers and items
* fixes keep-filters bug for desktop
* turns search tools into proper buttons on SM/XS
* fixes context/hierarchy icon display in default/result-list
* copies solr_ai/result-list over to fid_bdi and fixes icon display there too
* fixes result list display on XS
* improves filter checkbox display on XS