[BigQuery] TableId.setProjectId ignored if non-null value exists

[MMMarcy]

As per the title, calling setProjectId to an existing tableId instance is ignored if the existing projectId is not null.

Suggested changing this to:

  TableId setProjectId(String projectId) {
    Preconditions.checkArgument(!Strings.isNullOrEmpty(projectId), "ErrorMSG");
    return TableId.of(projectId, getDataset(), getTable());
  }

[andreamlin]

Hi MMMarcy, would you like to submit a Pull Request for this?