* Add some more checks to remove PHP warnings / notices.
* Adjust code to match CMS 9 API / interfaces.
* Do no longer use "query" but only searchTerm, as query is internal
API.
Search results are now processed through data processing by search
service. The result will be a SearchResult model from our domain. Also
SearchResult will execute new queries, e.g. from paginate widget,
through SearchService to apply data processing again.
Remove duplicate stub code to trait, to keep own logic and code clean.