MB-8363: implemented readers/writers settings UI

Change-Id: Ic202b1ef11205d5b8d820d66f1484c46948402dd
[stochmail@gmail.com: css/html beautification]
[alk@tut.by: minor css/html and commit message tweaks]
Reviewed-on: http://review.couchbase.org/26631
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>