Improved percent/URL-encoding

[tom-miseur]

Currently, the script generator produces code like this for application/x-www-form-urlencoded POST data:

address: "Street%20Address%201"

But, because we URL-encode values behind-the-scenes at runtime, we end up sending this unless the user modifies the generated code:

Street%2520Address%25201

We should attempt a URL-decode when we know the POST data may be encoded. I'll take a look at this myself but thought I'd log it here as well for comments.