The single validation module is split in multiple (simpler)
modules. In the process, we introduce one "validation worker" per
peer. This worker handle all the `New_head` and `New_branch`
advertised by a given peer. For so, it sends "fetching request" and
"validation request" to respectively the `Distributed_db` and and the
`Block_validator`. These two global workers are responsible of the
'fair' allocation of network and CPU ressources amongst the connected
'peers'.
Let's get serious. The full index of operations is not sustainable in
the production code. We now only keep the index of operations not yet
in the chain (i.e. the mempool/prevalidation). Operations from the
chain are now only accesible through a block. For instance, see the
RPC:
/blocks/<hash>/proto/operations
