Add more options to pass to "barman restore"

[rechtem]

The "POST: /servers/NAME/operations" allows a limited set of options to be passed to the barman restore command. For instance I'd like to pass "--staging-wal-directory".

This feature would add the possibility to pass options with attribute "options": "staging-wal-directory='blahblah';otheroption=...".

[martinmarques]

We are planning a new API directly embedded in Barman, which will have a 1-to-1 mapping with most, if not all, Barman CLI commands.