Create Single Screen Checkout process

[sanjeevyadavIT]

Describe the bugs
Currently the entire checkout process is made in a haste, and this has introduced lot of errors

1. No error message shown on Payment page if first and last name are not entered.
2. Button should be disabled on Address Page if required fields are blank
3. On payment page, if press back twice to enter Address Page, clicking the save button doesn't take you to shipment page.
4. Unable to place second order, right after placing order, due to checkout reducer state not reset
5. Show Payment Summary in Payment Screen
6. Refactor entire checkout process into single screen(address, shipping, payment, summary)

[sanjeevyadavIT]

@MehmoodArib Could you test these functionality,(by taking pull from develop branch), and make sure everything working ok

• On payment page, if press back twice to enter Address Page, clicking the save button doesn't take you to shipment page.
• Unable to place second order, right after placing order, due to checkout reducer state not reset