There's no obvious way to simply run a restic diff for the latest
snapshot against the previous one.
This simplifies the task to inspect the last snapshot changes. The user
only needs to run `sudo resticw --diff-latest` (optionally specifying a
profile).
This will allow to use `resticw` as a true wrapper, enabling to pass
restic options through it, for example:
```
resticw --profile profileX snapshots --compact
```
will now be suported by the wraper :)
