create payment_logs logger handler and use for logging payment changes with PaymentLogEntry and update tests to check that status changes are creating log entries BOOK-719
store log levels as uppercase BOOK-719
add some comments for the payments log handler class BOOK-719
remove patch for payment logger test BOOK-719
use wheel to install pip packages
refactor payment logger handler a little to import model when required
remove unused import BOOK-719
Merge pull request #943 from onepercentclub/feature/BOOK-719-updates

Updates for payment logging