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/json_tests/chain.rs

@@ -57,7 +57,7 @@ pub fn json_chain_test(json_data: &[u8]) -> Vec<String> {
 			};
 
 			{
-				let db = Arc::new(::util::kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
+				let db = Arc::new(::kvdb::in_memory(::db::NUM_COLUMNS.unwrap_or(0)));
 				let client = Client::new(
 					ClientConfig::default(),
 					&spec,