Making kio_http more accessible to RESTful clients

[Josef Spillner]

Hello,

to make the creation of clients to RESTful services possible, applications 
need access to HTTP response codes.
Since I'm not too familiar with the KIO code, I'm asking here first before 
putting in my patches from playground/libs/webtech.

- slavebase: Why is metadata discarded in the case of error()? It seems more 
useful to me to keep it.
- deletejob: It surely is an error that it creates a subjob and then dismisses 
the subjob's metadata?
- kio_http: Its desktop file only indicates reading capabilities, whereas 
writing and deleting is also supported. What's the reason behind this 
restriction?
- kio: What is the rationale for having specialised methods like 
KIO::http_post when all the functionality they include could be expressed by 
the existing methods? Such methods should be removed or put into convenience 
classes.

For KDE 5, my wishlist includes splitting the WebDAV code from the HTTP code, 
to make the class more maintainable and more useful for other HTTP-based 
protocols. Also, the API naming convention regarding metadata is very lousy, 
it is hard to differentiate between outgoing and incoming data, especially in 
KIO::Job::{setM,m}etaData().

Josef