Refactored pkg/netmap package provides JSON converters for
NodeInfo and PlacementPolicy structures, that has been used
by client applications.
It also updates Node structure itself so it is a part of
grpc <-> v2 <-> pkg conversion chain.
Signed-off-by: Alex Vanin <alexey@nspcc.ru>
Cleanup table is a cache for inner ring node to look for netmap
snapshot. It updates access time of bootstrapped nodes and will
be used to send `updateState` txs to clean netmap from unresponsive
nodes.
Signed-off-by: Alex Vanin <alexey@nspcc.ru>