The command line interface generally just does the command without checking whether it makes sense to Solaar, on the assumption that users of the CLI know what they are doing. When I fixed up the unpairing for Nano receivers I had to handle unpairing differently for Universal and Nano receivers so the low-level code didn't try to unpair for Nano receivers. This PR adds in a forced unpair and uses that version in solaar unpair <n>, restoring the old behaviour for the CLI.