Enable connection timeout per http call in http-verbs

Currently the timeout setting for services in application.conf is ignored. Instead, http-verbs (via ws) uses the Play's default setting (20 seconds).

https://github.com/hmrc/http-verbs/blob/master/src/main/resources/reference.conf#L15

We should enable to pass an (implicit) timeout parameter to all the http verbs, so that users can define different timeout values per REST call.
