Adds a Url property to the RemoteUpdater, which allows the remote url to...

... be updated.

This is a PR for issue #788 

Includes a single test case for verifying that the remote url was indeed changed.
Let me know if anything needs to be changed or corrected for this PR.
Good catch! I overlooked this in #567.

@sitereactor Could you please drop those `<remarks/>` where they appear?