Turns out, our getnextvalidators implementation already works the way
getcandidates is supposed to work, but original getnextvalidators works a bit
differently. It only returns validators, it doesn't return Active flag (all
of them are active) and it represents votes as a number. So for the maximum
compatibility:
* drop non-validator keys from getnextvalidators server-side
* drop Active flag client-side (sorry, it doesn't exist)
* allow unmarshalling old answers along with the new one
This technically breaks `query candidates` CLI command, but it'll be fixed
when getcandidates are to be introduced.
Note explicitly that transaction hash should be specified, so instead of
an old help text:
```
$ ./bin/neo-go query tx --help
NAME:
neo-go query tx - Query transaction status
USAGE:
neo-go query tx [command options] [arguments...]
OPTIONS:
--verbose, -v Output full tx info and execution logs
--rpc-endpoint value, -r value RPC node address
--timeout value, -s value Timeout for the operation (10 seconds by default) (default: 0s)
```
now we got the more informative one:
```
$ ./bin/neo-go query tx --help
NAME:
neo-go query tx - Query transaction status
USAGE:
neo-go query tx <hash> -r endpoint [-v]
OPTIONS:
--verbose, -v Output full tx info and execution logs
--rpc-endpoint value, -r value RPC node address
--timeout value, -s value Timeout for the operation (10 seconds by default) (default: 0s)
```
Implement a way to check if tx has been persisted on blockchain and
to get general info about transaction. Much more convenient than
handwritten curl queries.
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
