Moved tools/datapath.go to tools/datapath/datapath.go

Change-Id: Id9164529b2452b5074eed2d2489b3488458e9fae
Reviewed-on: http://review.couchbase.org/39659
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>