Inventory events lack important information

Description

Compared to price events, which are useful for re-indexing the content, inventory events are less useful in terms they are fired too often. Reindexing every time a customer places an order would be a waste, so most customers want to index the contents only when stock reaches a threshold, for example 10.

The current inventory events are fired with the current stock information. So it's impossible to know which kinds of changes were committed.