separate --no-thinning for source/target

[sblive]

it would be great to have separate --no-thinning for source/target.

Specifically I have a use case for --no-thinning-source:
*) multiple remote servers independently use zfs-autobackup just to create local snapshots and thin them. this ensures backups always exist locally (even if they are never pulled) and that server-specific schedules (e.g. thinning) can be implemented
*) a central backup server regularly pulls all of those servers and has a different (longer) thinning schedule locally (target). this provides more security (no inbound access) and central control (e.g. over timing etc.) vs the remote servers pushing those backups.

I guess it should be possible to first sync with --no-thinning and then call with --no-send again (or something similar, untested), but I think it would be nice and reasonably easy to implement 2 new switches (keeping --no-thinning as is), like for schedule.

Thanks!

[psy0rz]

we can do that :)