CBQE-2418: add ui xdcr tests, advanced settings

Change-Id: Iaefa644e8758e6a35b4a41e4ebce13c72ea32933
Reviewed-on: http://review.couchbase.org/41794
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>