public Container searcher(String chainName, Class<? extends Searcher> searcher, ConfigInstance... configs) {
                return searcher(searcher.getName(), chainName, searcher, configs);
            }
@param chainName chain name to add searcher
@param searcher  add this searcher to the search chain
@param configs   local searcher configs
@return builder
application/src/main/java/com/yahoo/application/Application.java