Rework: shared memory

Right now, we pass a block of hashcodes to new machines. Instead, we could send ALL blocks of shared memory that we have, i.e. the meta block and the trie structure. This is a bit more expensive on the sending part, but re-constructing the trie on the new machine then becomes a matter of some memcpy-calls. This might be useful when considering spot-instances.

I would prefer if the proxy was the only component with write access to the shared memory.