Ability to deliver packaging patches

[PVince81]

In case of updater mess up, sometimes it might just be a matter of providing a repair step of some sorts or cleaning up files that were left over.

One idea would be to have the repair part be delivered as an additional patch that would be downloaded additionally to the tarball. The patch would be only for bugs related to the updater and nothing else (no security, no last minute bugfixes)

The patch would need to be signed.

@VicDeo @DeepDiver1975

[VicDeo]

@PVince81
It can be done with autoloader.
Just by adding an empty dir that has higher priority. Thus, all overriden classes will be loaded form this directory and are wiped as soon as update is done.