asset: bitmask type optimisation (#922)

* asset: basic optim. bitmask

* glorious: nits

* currency: forgot parralel in testttttt

* ticker/orderbook: test fixes

* engine/rpcserver: fix and expand tests

gctscript/wrappers/validator/validator.go

@@ -180,7 +180,7 @@ func (w Wrapper) CancelOrder(ctx context.Context, exch, orderid string, cp curre
 	if !cp.IsEmpty() && cp.IsInvalid() {
 		return false, errTestFailed
 	}
-	if a != "" && !a.IsValid() {
+	if a != asset.Empty && !a.IsValid() {
 		return false, errTestFailed
 	}
 	return true, nil

gctscript/wrappers/validator/validator_test.go

@@ -105,7 +105,7 @@ func TestWrapper_CancelOrder(t *testing.T) {
 	}
 
 	_, err = testWrapper.CancelOrder(context.Background(),
-		exchName, orderID, cp, "")
+		exchName, orderID, cp, asset.Empty)
 	if err != nil {
 		t.Error(err)
 	}