webclient search is fired synchronous.. make it async

[Malte]

Scenario is:
The "Wikidata Search"-Mode fires search to a remote database which may take a while to return and here I would like to render a spinning wheel (likewise to after triggering "Import claims".

Right now, the implementation should render a spinning wheel in the page panel directly after the search is fired but this is never appears to the user because the search request blocks the browser/ui (from updating/refreshing).