[FEATURE] Indicate a loss

[waschinski]

Sometimes it happens that a user seems to forget to book out a drink and doesn't even remember he didn't, so it would be helpful if you could indicate a loss so stock values are correct again.

Optional it would be nice to be able to:

• book the loss on a certain user (similar to Manually book products for user #9)
• divide the cost of the loss on all active users

[boerniee]

Alternative:
Show a list of persons which have consumed this product in the last 30 days and select the users to which the loss should be billed.