Feature Request: Enable easy changing of the Feed URL

[jaxaCe]

I recently noticed that some RSS feeds that I had subscribed to a long time ago had not been updated for a few weeks.
The reason was that the URLs were no longer correct and returned HTTP 404 errors.
Changing the URL of a feed is currently not possible. Instead, a new feed has to be created and the old one deleted even though it was basically the same feed.
The URL should be changeable, so that such problems could be easily solved.