Add setting for traditional buildQueryString

buildQueryString in aurelia-path has tradidional argument which triggers different way to format query params.

Currently HttpClient doesn't have similar param, therefore I have to build the query manually and append to url instead of using withParams RequestBuilder method.

Start by comparing aurelia-path's buildQueryString traditional argument with the HttpClient RequestBuilder's withParams path. Trace how query parameters are currently formatted and determine where the setting belongs; done means callers can select traditional formatting through HttpClient without manually appending the query string.

Written by the indexing model from the issue text.