One reciever for several comments

[LevZed]

Now several receivers are used for different comments, but it is possible to use one receiver.
We can't just compare the received message with a string, but we can use the following construct:

msg.asSlice().hash() == "str".asSlice().hash()

Here is the receiver for a simple counter contract:

    receive(msg: String) {
        if (msg.asSlice().hash() == "increment".asSlice().hash()) {
            self.counter = self.counter + 1;
        } else if (msg.asSlice().hash() == "decrement".asSlice().hash()) {
            self.counter = self.counter - 1;
        } else {
            reply("Invalid command".asComment());
        }
    }