Use exponential backoff for updates

[ghost]

If an update fails, we should delay the next update exponentially, as otherwise we'll repeatedly perform updates on a fixed interval while the network or service is degraded. Additionally, we should also not wait too long after the first failure, as the issue may be ephemeral and we should not persist a degraded or stale state.

[DXTimer]

Since the plugin carries out periodic syncs we should factor in the refresh rate and depending on the refresh rate it may be more prudent to abandon the current refresh cycle if it fails more than X times.