Add generic views: pt1

[Ramin-RX7]

(this has to be done on feature/generic-view branch that already exists. No pull request is needed)

Implement the given views using django generic views:

main:

• Index page
• About us page

foods

• category list
• category details
• food details
• menu

orders

• index
• order list
• order details

[EliBabakhani]

done