Rename `unite-wallet` to `unit-e-wallet` after 0.18 sync

[cornelius]

According to our naming scheme we use unit-e in executable names. The upstream merge with Bitcoin Core 0.18 adds a new executable which isn't covered by clonemachine yet, so it currently is named unite-wallet. To be consistent we should rename it to unit-e-wallet (and adapt clonemachine accordingly).

This issue depends on the merge of the 0.18 code (#1041). It should be done after this has happened.