core, core/state, trie: EIP158, reprice & skip empty account write

This commit implements EIP158 part 1, 2, 3 & 4

1. If an account is empty it's no longer written to the trie. An empty
  account is defined as (balance=0, nonce=0, storage=0, code=0).
2. Delete an empty account if it's touched
3. An empty account is redefined as either non-existent or empty.
4. Zero value calls and zero value suicides no longer consume the 25k
  reation costs.

params: moved core/config to params

Signed-off-by: Jeffrey Wilcke <jeffrey@ethereum.org>

core/state/sync_test.go

@@ -60,7 +60,7 @@ func makeTestState() (ethdb.Database, common.Hash, []*testAccount) {
 		state.updateStateObject(obj)
 		accounts = append(accounts, acc)
 	}
-	root, _ := state.Commit()
+	root, _ := state.Commit(false)
 
 	// Return the generated state
 	return db, root, accounts