getScriptSig method
This method must be implemented by all subclasses. It must return a valid unlocking script a.k.a scriptSig
Implementation
@override
SVScript getScriptSig() {
var multiSigs = signatures.fold('', (dynamic prev, elem) => prev + sprintf(' %s 0x%s', [HEX.decode(elem.toTxFormat()).length, elem.toTxFormat()]));
return SVScript.fromString('OP_0 ${multiSigs}');
}