Use .fa-check in place of .fa-ok, and .fa-reorder in place of .fa-bars
balance due if payment is less than order total

also had to fix some other logic to fix the specs after my changes, I noticed
there are some issues that this might affect #4563 #4550 #4605

Fixes #4637
Fix payment state on backend orders/payments_spec
Updating price must touch variants to bust cache.
Update item count and totals on Order#merge!

Fixes #4610
Merge branch '2-2-stable' into 1838