Improve inventory counting

* Remove the old ProductCountgDialog and replace it with InventoryCountWizard
* The new wizard is capable of doing both manual counts (like the way we did
  before) and assisted counts (using a barcode scanner)
* With those modifications, it's possible now to do an inventory for batch
  items too

Change-Id: I2ee68abda567b29725c5a6cd88440dcd93f1dae5
Merge "Improve inventory counting"