Combine FindCouchbaseErlang.cmake with ns_server additions

Change-Id: I9778a25244eae08d13c822dfb21d11123c17ae9a
Reviewed-on: http://review.couchbase.org/35038
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>