accepts url strings or paths; allows specifying path to body

closes #497 and #498. You can now use webRequest to hit literal url strings or paths to urls found in incoming messages:

* as string with Url rule: "http://localhost:7070/library"
* as path to url in incoming json with UrlPath rule: ".url"

You can also specify the scope of the request body to be sent via POST or PUT:

* BodyPath rule: defaults to "." but could be ".Something.Specific"

updated tests adding examples for both UrlPath and BodyPath with GET and POST requests.