Implement advanced upload packing via RHP4

[ChrisSchinnerl]

With RHP4 we can have workers upload partial sectors to hosts immediately and without packing.
The worker should then inform the bus about the uploaded sector.

The new pinning loop of the bus will then use the RPC for merging sectors to merge partial sectors together.
After merging the packed sector will be pinned.

That way we can get rid of the extra persistence we currently have in the Bus meaning that backups become as easy as only backing up the database again.