HTTP internals: move some methods inside HTTP request class

... from the private to the public class, because we need to access
these methods from other classes.

Change-Id: I2c5ea84e0f5d3641c1dc02342348f1022d886249
Reviewed-by: Richard J. Moore <rich@kde.org>
HTTP internals: introduce protocol handlers

... to defer the decision which protocol will be used on a specific
channel. This is to allow using the SPDY protocol instead of HTTP (to
be implemented in a later commit); which protocol will be used can
only be decided after the SSL handshake.

Change-Id: I6b538320668fe4994438f0095ecdc445677cf0a6
Reviewed-by: Peter Hartmann <phartmann@blackberry.com>