Support redirection with online repositories

If update server is implemented to use redirection to point to the actual file in another location (this could happen because of authentication or for load balancing reasons), IFW fails to download files properly.

For example, set up server which redirects everything to another location. Add that as the remote repository and test it in IFW using the Test button. It says it fails to parse Updates.xml file, probably as it didn't get the right content since it didn't follow the Location header.

What it could do is follow the redirection to download the real file. ie. if Location header exists in the reply, do the request to that.