MB-8241: Move MapReduce View specific stuff into its own record

Change-Id: I2848abbc0338790d0b3488d66eac173c9a477585
Reviewed-on: http://review.couchbase.org/26240
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>