Convert errors page to haml
More intelligible error message for payments
Improved error message content on payment page

[#40820451]
Make payment page layout robust to error messages

Fields were not appearing on the correct lines
after error messages appear.

[#40820451]
Human-readable Stripe error messages

[#40820451]
Round trip field values

So users won't need to re-enter them after errors

[Finishes #40820451]
Show summary only instead of redundant global errors

[Finishes #40820451]