Fixed some object having different behaviour than the pure-data ones and fixed some bugs

Add BANG message support for objects MessageAdd, MessageSubtract, MessageMultiply, MessageDivide and MessagePow so they have the same behaviour that the pure-data ones

Fixed MessagePow returning wrong values for a power <= to 0

Fixed some other bugs aswell
In this case I would usually suggest a `switch/case`, such as:
```C
switch (message->getType(0)) {
  case FLOAT: {
    last = do work
  }
  case BANG: {
    send message with last
  }
}
```