Refactor Checkout

* Remove the inverse dependence on nereid_payment
* Use the payment_gateway modules
* Allow using payment profiles and storing credit card info
Merge pull request #18 from sharoonthomas/develop

Refactor Checkout
Bump version to 3.0.2.0dev1
Fixed flake8 issues
Merge pull request #20 from GauravButola/feature/task-4203

Fixed flake8 issues #4203
Refactoring for Flask-Login
Merge pull request #22 from sharoonthomas/develop

Refactoring for Flask-Login
Replace urls.xml with nereid(3.0.7.0) route
Merge pull request #26 from tarunbhardwaj/develop

Replace urls.xml with nereid(3.0.7.0) route
Release version 3.0.2.0
Merge branch 'release/3.0.2.0'