rpc: fix Signature parameter unmarshalling
It is based64 encoded and decoded, see
5108d1c2c7/pkg/smartcontract/parameter.go (L78)
and
26d04a642a/src/neo/SmartContract/ContractParameter.cs (L150)
and
26d04a642a/src/neo/SmartContract/ContractParameter.cs (L79).
Also, TestInvocationScriptCreationGood is extended and compatibility
is tested with the following C# node requests:
```
anna@kiwi:~/Documents/GitProjects/nspcc-dev/neo-go$ curl -d '{ "jsonrpc": "2.0", "id": 1, "method": "invokefunction", "params": ["50befd26fdf6e4d957c11e078b24ebce6291456f", "a", [{"type": "Signature", "value": "4edf5005771de04619235d5a4c7a9a11bb78e008541f1da7725f654c33380a3c87e2959a025da706d7255cb3a3fa07ebe9c6559d0d9e6213c68049168eb1056f"}]] }' seed1.neo.org:10332 | json_pp
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 665 0 381 100 284 197 147 0:00:01 0:00:01 --:--:-- 344
{
"jsonrpc" : "2.0",
"id" : 1,
"result" : {
"notifications" : [],
"stack" : [],
"script" : "DGDh51/nTTnvvV17TjrX3bfl3lrhztr1rXVtvvx7TTznjV/V1rvvbl/rnhzfffzRrdzzt7b3n1rTbl1rvTp3vbnlxvdrd9rTt5t71zrnn13R317rbXdzrzTj3Xrx5vXTnp8RwB8MAWEMFG9FkWLO6ySLBx7BV9nk9v0m/b5QQWJ9W1I=",
"exception" : "Called Contract Does Not Exist: 0x50befd26fdf6e4d957c11e078b24ebce6291456f",
"state" : "FAULT",
"gasconsumed" : "104526"
}
}
anna@kiwi:~/Documents/GitProjects/nspcc-dev/neo-go$ curl -d '{ "jsonrpc": "2.0", "id": 1, "method": "invokefunction", "params": ["50befd26fdf6e4d957c11e078b24ebce6291456f", "a", [{"type": "Signature", "value": "Tt9QBXcd4EYZI11aTHqaEbt44AhUHx2ncl9lTDM4CjyH4pWaAl2nBtclXLOj+gfr6cZVnQ2eYhPGgEkWjrEFbw=="}]] }' seed1.neo.org:10332 | json_pp
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 591 0 347 100 244 794 558 --:--:-- --:--:-- --:--:-- 1352
{
"jsonrpc" : "2.0",
"result" : {
"state" : "FAULT",
"exception" : "Called Contract Does Not Exist: 0x50befd26fdf6e4d957c11e078b24ebce6291456f",
"gasconsumed" : "104526",
"notifications" : [],
"stack" : [],
"script" : "DEBO31AFdx3gRhkjXVpMepoRu3jgCFQfHadyX2VMMzgKPIfilZoCXacG1yVcs6P6B+vpxlWdDZ5iE8aASRaOsQVvEcAfDAFhDBRvRZFizuskiwcewVfZ5Pb9Jv2+UEFifVtS"
},
"id" : 1
}
```
171af36ead