Add support for listing and removing remotes

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Bump everything to sha256

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Hide the server password and fix some error handling

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>