cluster settings RAM Quota similar to what we have in wizard

Change-Id: Iaf53e0d56860729170eb683495e190b8023996fd
Reviewed-on: http://review.couchbase.org/32442
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>