Add getFullUri

[k-bx]

This might not look "perfect" in terms of API, so this PR is rather a starting point for a question in advice on how to do this best.

I need to debug, which URL am I querying, and currently there seems to be no way to just print URI with parameters that will be requested.

I have to admit, I couldn't get down to the very http-client source which does the request itself, so I can't say for sure if this show (getRequestUri req) == actual requested uri, still, this function is useful enough to work for me, so I think it might be fine as is already.

Thanks.

[k-bx]

As an idea, it could be very useful to have a way to get a curl string for any request (POST, GET and others).