Better url-param and body handling

**immanuel.hayden** ([Bug 55256](https://bz.apache.org/bugzilla//show_bug.cgi?id=55256&redirect=false)):
As I wrote down 55255 I thought:

Generally it would be cool if it would be possible to set the url-params and body separately instead of having to write the url-params in the address bar when doing a POST request. Like instead of now "Parameters" and "Post Body" having "Url Params" which is the old Key/Value, and then "Body (Key/Value)" and "Body (Raw)" which are mutually exclusive (or more exactly, the key/value being a sort of wizard/formater for the other).

OS: All