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/spec/spec.rs

@@ -667,7 +667,8 @@ impl Spec {
 	/// constructor.
 	pub fn genesis_epoch_data(&self) -> Result<Vec<u8>, String> {
 		use transaction::{Action, Transaction};
-		use util::{journaldb, kvdb};
+		use util::journaldb;
+		use kvdb;
 
 		let genesis = self.genesis_header();