Updates to DuplicatiVerify.py
Updates to DuplicatiVerify.py

* Increase block size ro 8MB to make the process faster and still light on
  memory on a low memory machine
* Added a --quiet argument to reduce very verbose output.

mnaiman/duplicati,mnaiman/duplicati,duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,duplicati/duplicati,duplicati/duplicati,duplicati/duplicati,mnaiman/duplicati,mnaiman/duplicati