sandbox: handle snap not permitted error

[pastaghost]

In Card::handleSubmit(), check to see if action.callback(params) (this wrapssendFlaskRPCRequest() in most cases) returns an object of type JsonRPCError. If this is the case, parse the error code to check for code 4100 (snap not permitted.) If error code 4100 is returned, display an error toast to the user with instructions to install the snap instead of piping the error message to the card output group.