Follow-up improvements for consumer offset reset tool (KIP-122)

1. We should try to ensure that offsets are in range for the topic partition. We currently only verify this for the shift option.
2. If you provide a CSV file, you shouldn't need to specify one of the --all-topics or --topic options.
3. We currently support a "reset to current offsets" option if none of the supported reset options are provided. This seems kind of useless. Perhaps we should just enforce that one of the reset options is provided.
4. The command fails with an NPE if we cannot find one of the offsets we are trying to reset. It would be better to raise an exception with a friendlier message.