Some commands don't accept arguments, but users try giving them and don't
notice a mistake. It's a bit more user-friendly to tell the user that there is
something wrong with the way he tries to use the command.
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>
