Need an endpoint for getting the latest sequence ID

[bardram]

Right now sequence IDs are enforced - see #375 .

If this is the case, we need a way to get the latest sequence ID for a data stream, so that we can continue from there (and avoid the error).

[Whathecode]

Yup. This is missing information which most likely belongs in deployment status.

When you redeploy a device, you need to know from which sequence ID to start uploading data.

In normal operations, though, it is the client who locally track that state, as it is the client who determines sequence IDs.