OP-1304 | Enhance product selections in edit inventory

[ArnaudFofou]

See OP-1304.

[mwithi]

Although the feature is doing what expected, there is room of code improvements, please read the comments

[dbmalkovsky]

There needs to be a review of the whole file of InventoryEdit not just the recent changes. For example, there are other occurrences that should be using isEmtpy(); there are allocations where <> should be used instead of the type; there are occurrences where Boxed types (specially Integer) is being compared with == instead of equals(), etc.