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/tests/trace.rs

@@ -27,7 +27,7 @@ use client::*;
 use tests::helpers::*;
 use devtools::RandomTempPath;
 use client::{BlockChainClient, Client, ClientConfig};
-use util::kvdb::{Database, DatabaseConfig};
+use kvdb::{Database, DatabaseConfig};
 use std::sync::Arc;
 use header::Header;
 use miner::Miner;