Adds item discount route
New styles for discount and storage pages
New javascript files for discount and storage pages
Minor changes to  ItemStorage and itemDiscount views
Adds shop_discount_edit service
New validation messages for discounts
Adds onDelete="cascade" to ItemsDetails column
Removes unnecessary use.
Minors changes to findItemByStatysAndItemsdetails method
Removes itemName field and its methods
Changes to methods according to database changes
Changes to methods according to database changes
New quantity field and its getter and setter
New item discount form
New discount management method