Reorder level report update - Production plan fix

Updated the Itemwise Recommended Reorder Level to enable the selection of several Item Groups. Also added an "item" multiselect filter to only show the items you want.

Updated the Production Plan to make sure, if you have selected the "get items from: Material Request" option, that every "po_item" you select is related to a Material request. Otherwise, the Production Plan could not be completed if you chose several items.