Include durablity man page into the dist

Change-Id: I8ae2956b991b183c1fe94909f46dc03f5248fff1
Reviewed-on: http://review.couchbase.org/28012
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>