(Bug 4862) Don't lowercase POST args

We have an argument for lowercasing GET args (normalizing input, since
this can be so easily entered by hand, and we don't have anything that's
case-sensitive). But we need to leave POST args alone. Widgets use
case-sensitive names for their form elements, e.g.,
Widget[WidgetName]_...
Merge pull request #245 from afuna/create-oops-bug4862

(Bug 4862) Don't lowercase POST args