Slower performance when creating batches with many entries

[youhavethewrong]

I've noticed that file generation slows down significantly when adding many entries into the same batch. I've created a pull request with a suggestion of removing the updating of batch counts and totals on every addEntry() call and instead doing it when the user wants with a new updateBatchValues() method. This way, those who have a use case to update the counts and totals after every addEntry() call can still do so, while those who only need those totals updated at the time of generateFile() can realize much better performance.