dissolve util (#7460)

* ethereum-types refactor in progress

* ethereum-types refactor in progress

* ethereum-types refactor in progress

* ethereum-types refactor in progress

* ethereum-types refactor finished

* removed obsolete util/src/lib.rs

* removed commented out code

ethcore/src/tests/client.rs

@@ -25,8 +25,7 @@ use ethereum;
 use block::IsBlock;
 use tests::helpers::*;
 use types::filter::Filter;
-use bigint::prelude::U256;
-use util::*;
+use ethereum_types::{U256, Address};
 use kvdb_rocksdb::{Database, DatabaseConfig};
 use devtools::*;
 use miner::Miner;