[FEA] Providing progress bar / any indication of steps for fit and transform

[bschifferer]

Is your feature request related to a problem? Please describe. As a user, I can execute a NVTabular workflow on a large dataset (billion of rows) and even with 4x GPUs on NVME raid, the fit function can take 30-45min (or longer).

It would be great, if we can provide any kind of progress bar / steps during fit and transform. (e.g. # of files progressed, chunks, ops, etc.)