Separate migrations from util (#6690)

* separate migration from util and make its dependencies into libs:

* snappy
* kvdb
* error
* common

* renamed common -> macros

* util error does not depend on snappy module

* ethsync does not depend on util nor ethcore_error

* nibbleslice and nibblevec merged with patricia_trie crate

* removed unused dependencies from util

* util journaldb traits does not need to be public

* util_error

* fixed ethcore compile error

* ignore .swo files

* Update chain.rs

ethcore/src/trace/mod.rs

@@ -39,7 +39,8 @@ pub use self::types::filter::{Filter, AddressesFilter};
 
 use bigint::prelude::U256;
 use bigint::hash::H256;
-use util::{Address, DBTransaction};
+use util::Address;
+use kvdb::DBTransaction;
 use bytes::Bytes;
 use self::trace::{Call, Create};
 use vm::ActionParams;