Working Routes for Disease

@kalamoni @mostafa-adel @FatmaEmran @sedramina @tonyfoti @mohamed-halawa 
There was no views or controller for disease in this commit, we should have a working disease model with all its views and the routes are configured directly. however, I still haven't coded the part where the retailer can add items (or relate items) to the disease whether recommended or restricted.
please review and thanks in advance.