Move the data from extentions (like ReqData<T>, but not Clone)

[RoDmitry]

Implementation of new ReqDataMove<T> (like ReqData<T>, but not Clone): request_data_move.rs

For example, if I pass my data from middleware, and in my request handler I need an owned value. I think this is very much useful, because Unlike app data, request data is dropped when the request has finished processing (quote source). So I don't understand why would I need Rc<T>, and where else would I need to use my data, if I would have used ReqData<Rc<T>>. Maybe give me examples?
Also if you need to mutate it, it's also easier (because it's owned), and you can later re-insert it back into the extensions map, so you will always have exactly one copy of the data. And if you have forgotten to re-insert it, and you use it elsewhere (but where can it be?), you will get a compile time error (I guess).

Can make it look better and send a PR

[robjtede]

It's an interesting idea. I'd consider a PR to actix-web-lab for this.