Remove parent stock quantity for variants. Each variant should have its own stock quantity.
When displayed in an item list in admin area, a product with variants should be displayed as a specific variant (the default variant, if present, or the first one, if the default variant has not been set). This product should also have a link displayed next to it with information like the following: "Variants: 4. SKUs: Sku1, Sku2, Sku3, Sku4. Total QTY: xxx". By clicking this link, a panel should be expanded below with data on all the existing variants of the product loaded with AJAX.
Add the ability to search for variants by SKU, with search results displayed as described above.